Chapter 33
"Papa."
Bucky lifted his head groggily and attempted to smile at his son. "Yeah, buddy?"
"Play now."
He sighed and looked down at the pile of blocks that had been dumped unceremoniously in front of Bucky's feet by his son. "What do you want to build, Yashka?"
"Big house. No scary man. Полохой че'век уходи! (Bad man go away!)"
"Yeah, that sounds pretty good, buddy. Мы должны держать всех плохих парней подальше, не так ли, Яшка? (We gotta keep all the bad guys away, right, Yashka?) We don't want any scary men in our house, do we? Ok, lemme get down there with you. How tall do you want the walls?"
"Big. Like papa."
"Well, that's pretty big, huh? Для этого нам понадобится много игрушечных блоков, приятель. (We're gonna need a lot of toy blocks for this, buddy.) I don't know, what about big like Yashka?"
The little boy laughed and squealed at Bucky's tickling, saying, "Papa."
"Ok. Let's see. How about this tall?"
Jamie giggled. "Больше, папочка! (More, Papa!)"
"More? Wow. We're gonna need a crane to build it any bigger. How about…this tall?"
"Ok, papa."
"Good. Хорошо, умный мальчик. (Good, clever boy.) Let's put the blocks all the way around now. Ok?"
In between casually watching his son clumsily pick up and place bricks in a loose square, Bucky looked over to the pink-festooned cot where his daughter was sleeping. He had barely left the room where his children slept and played for two days, except to sleep. Thea had been giving him space to be alone with the children at his request, but he could see how much it was bothering her. He'd never avoided her before, not like this. He had particularly been unable to ignore how fearful she was earlier that morning when she brought him his eggs and kasha. He was in a terrible place emotionally and it wasn't getting much better, as he knew what had to be done soon.
"Papa! Papochka. Постройте дом! (Build the house!)"
Bucky looked down at Jamie and smiled sadly. "Sorry, buddy, I was looking over at your sestrenka. Papa has to keep an eye on her, too."
Jamie frowned and shoved a toy brick at Bucky's hand. "Build now."
"Ok, ok, pal. You got it. Let's see. We need a huge gate and door, right?"
"Yellow."
"Uh, do you think we have enough yellow blocks, Yashka? I don't know if we do."
Jamie shoved some of the pile closer to Bucky and repeated, "Yellow."
"Well, we can start it yellow anyway. So, who is going to live in this house, buddy?"
"Mummer, Papa, Jamie, Ses'renka."
"Sounds good. What about Tetya Mary-Claire and your cousins?"
Jamie frowned. "No more."
Bucky sat back so his head was propped against the side of the sofa. "They are our family, Jamie, so we want to live with them. When Dyadya Styopa gets to come home, he'll live with us, too."
"No."
"Sorry, buddy, but that actually isn't up for debate, Yashka. We are all going to live in the same house."
"Noooooo. Papa. Mummer. Baby. No Dyadya, no Tetya. No! No scary man!"
Bucky picked up his son and placed him on his legs before resting his head lightly on top of his son's dark brown curls. "You know perfectly well that Steve isn't the scary man, Yashka. He is your Dyadya Styopa, who pushed you in the tree swing at Arnwell and carried you on his shoulders when we walked down to see Dyadya Richard's horses. He's a good guy, pal. Promise. And I'm not going to leave you. They said that Papa can stay now. Ok?"
"Papa sad."
"Yeah, Yashka, but it's ok. It's ok. I love you, little buddy."
"Love Papa."
Bucky wrapped his arms around his son and said in a shaken voice, "I love you very much, buddy. So much. It is going to be ok."
Jamie insisted urgently, "Mummer sad."
"Yeah, I know, buddy. There is a lot going on right now, ok? And you've got a new brother that's gonna be born in a number of months, so Mummy feels a bit sick sometimes. It will be fine though. She felt that way when you were born and look how great you turned out. Ты наша гордость Яшка. (You are our pride, Yashka.)"
Jamie seemed very unconvinced, but he didn't squirm or wiggle in Bucky's arms.
"Shall we finish building this big house now? Big and tall with a yellow door?"
"Yes."
"Then maybe we can call in Mummy and see what she thinks."
"Want Mummer now."
Bucky nodded. "Yeah. Yeah. OK, I can go and call her in."
"Papa stay."
"Yeah, both Mummy and Papa will stay in here, buddy. Sound good?"
"Ok." Apparently satisfied, Jamie looked back down at the blocks and began pushing one of them around. Bucky opened the door to the children's nursery and stood in the corridor awkwardly.
He frowned at Gleb, who was pacing at the far end of the corridor, since he had believed that Shurik was the one scheduled for house duty. Yet, Bucky's focus was still on finding Thea, as he called out, "Bella? Krasotka?"
There was a flurry of movement across the corridor in the bedroom, the door flung open, and suddenly Thea was in front of him with a worried, anxious expression. "Is everything ok? Did Winnie wake up?"
Bucky tugged her close to him and said gruffly, "She's still sleeping, baby. Everything is fine. Yashka wants us both in there, so I thought why not?"
"You don't mind me coming in for a while? I know you were wanting some time with just you and Jamie."
"Baby, I'm sorry. I didn't really intend to exclude you. I just needed to feel like I could be alone with my children. I needed to be with them without someone mediating like I was a monster. Somehow that became pushing you away and I'm sorry."
Thea nodded. "Do you feel better?"
"A little. Will you stay now, baby? I'm done sulking. Promise."
Thea looked down at the ground and took a deep, uneasy breath. Then, she said cautiously, "You know, I have been trying to decide when to come in to talk to you. Something important has happened, Yasha."
Bucky peeked back through the door at Jamie, who was still stacking the blue blocks into walls, then said carefully, "Ok. What is it?"
"The president issued a pardon for Steve this afternoon. So, there is not going to be any court-martial after all. Since they were still at the Article 32 stage of the process, he was never formally charged, so he will be allowed to receive an honourable discharge. That means that Steve is coming home soon."
"Черт возьми! Holy s***, Bella, and you didn't come in to tell me that?"
"I didn't know about it until about an hour ago, Yasha. Mary-Claire has been out doing whatever it is she's doing. I have been trying to get everything ready. As soon as she gets back, then things are going to get serious. They are having some big meeting, so I've been trying to sort out the food and everything."
"You should have come to find me. I needed to know this."
Thea stepped back and said coldly, "If you say so, Yasha. Anyway, you know now. Does that mean that you're going to go off and do a perimeter check on the property and talk with the security team? Or are you still going to come play with Jamie and me?"
Bucky narrowed his eyes angrily at her, but said stiffly, "I promised the little guy that I'd stay in there. I'm not breakin' a promise to him."
"Well, then, let's go and see what we are building."
"A big house, apparently, where he only wants the four of us to live."
"Poor darling. He's so afraid that you're going to disappear again, Yasha."
Bucky nodded his head and replied roughly, "I know. He has every reason to be frightened and insecure, poor kid."
"Yes, he does. However, that doesn't mean that we cannot make things right. He needs stability and he needs love. He's going to get that from you, isn't he?"
"Yes. I'm not going nowhere, Bella. They said that I'm a free man, so I'm gonna use that freedom to spend my time taking care of you and the children."
"That is exactly what I have told Jamie, you know. I believe in you, Yasha. Have they talked to you about my status?"
He grunted angrily. "Yeah."
"I see. Is it like we thought?"
"Yes."
Thea sighed angrily. "Mary-Claire says that they don't actually have any standing on which to proffer charges against me, you know. And, legally and publicly, you are an innocent man. That means that you're a highly decorated veteran and POW. How are they going to force you into doing anything for them, Yasha?"
"Because we wanna keep things this way, baby. They know that I'm not stupid enough to believe that they couldn't turn things on me if they wanted to. If I wanna keep you and the kids safe, then I gotta play ball. Steve said the same thing, so I know he's expecting this both for me and for him."
"Ok. Right, so, does that mean that you're going to have to work with them all the time?"
Bucky shrugged miserably. "I don't know, baby. It might. Come on. Let's go in and play with our kid, huh? I don't wanna talk about any of that other cr** right now."
She nodded and let him take her hand.
"How long will you be gone, Yasha?"
"I don't know. He didn't say how long this would take. Could be a couple of days for all I know."
"And you're sure no one will know that you are gone? If they find out then it could be quite bad."
"No, I'm not sure, but this is too important a mission to quibble about the risk. Even though I don't like to talk about it, I am the deadliest assassin the world, Thea, so I do have a fair few useful skills that I can use for this mission. You don't think that the Winter Soldier was called a ghost because I had any trouble slipping into and out of wherever I needed to go to take down my target, do you?"
Her expression instantly both fearful and angry, Thea whispered, "You don't have to be such a berk about it, Yasha. I'm just worried."
Bucky growled and possessively put his arm around her, as he explained harshly, "Look, I cannot change what has to happen here. I don't want to do any of this, but it isn't up to me, Thea. I'm sorry that I'm being such a jerk, but I'm angry and this really is the best that I can control myself at the moment. I know that I've been treating you like s*** these last few days, Bella, and I've hated myself for it. You deserve better, krasotka. However, I AM going to come back to you even if I have to drag myself here by the fingernails. Whatever fallout there might be from this mission, it will not include anyone separating me from you and the children even if I have to hide us in Wakanda again."
"Oh. Well…ok, I suppose. What is going to happen tomorrow?"
Bucky released his firm grip on Thea and turned to begin pacing the space between the bed and the long wardrobe on the far wall. "We're going to fly with Mary-Claire to meet Steve when he does the White House ceremony. Then, you'll go back with them and I will disappear up to Westchester. Xavier has given his word that his own people will be in place here both as extra protection and as diversions if necessary. This is the best time to do this, Bella, since everyone will expect me to be glued to Steve's side from the moment he's released. They would not think that I'll run off and leave you alone either. This is the time that my absence would be least noticed. Also, there may be less invasive supervision for at least the first 24 hours, since Steve should be given a grace period to reunite with his wife and children. I need to take advantage of this."
"But…why, Yasha? What is so important? You never even mentioned this Xavier before yesterday. I don't understand."
Bucky looked at her with pained, desperate eyes and sighed. "Do you remember that evening in Constanta? How I was prepared to force the tsygane to return what was stolen?"
"Y-yes, of course I remember that day. It was horrible."
He shook his head angrily, his long dark hair whipping across his face so his expression was hidden. "It was not just your papers that I needed returned. There was one other thing that was important enough to retrieve that I was prepared to kill for it. Now that I have deposited it somewhere safe, I am going to make certain that item's hiding place can no longer be found."
"Was it that little wooden box with the strange symbol on the top?"
Shocked, Bucky's head snapped back up and he watched her for a moment before he replied, "Yes."
"I always got the feeling that I was forbidden to ask about that box. Where is it now?"
"I know where it is. You do not, nor can you. I have hidden it where it cannot be retrieved without someone dying. Even with the Hydra Discount Brand Serum, I almost died. But that was where I was told to hide it, so I did. Now, unfortunately, I'm going to go let someone play with my memories again."
Thea narrowed her eyes and asked, "This Xavier isn't some HYDRA scientist, is he?"
"No, krasotka. Nothing at all like that. He is a mutant with unbelievably strong telepathic abilities. Ordinarily, I would do nearly anything to stay out of the range of powers like Xavier's. However, this mission is too important for my likes and dislikes to matter. According to the person who gave it to me, the contents of that box must remain hidden or quite literally half the world will die."
"Yasha! That battered little wooden box? How is that possible?"
"All I can say is that the box isn't what it looks like, Bella."
"And Xavier can destroy it or something?"
Bucky breathed out through his nose sharply and said uneasily, "No, Bella, it cannot be destroyed. Not really, anyway. It is complicated. When I return, I will no longer know where I hid it. You don't know. Xavier is the only person who will, but that is part of the plan."
"Can you trust him with this knowledge?"
"I don't know. This isn't my plan. I'm following the mission that was given to me. I was supposed to hold on to this box until the opportunity to meet Xavier arose naturally. I wasn't supposed to seek him out before I had an opening."
Quite clearly fearful, Thea demanded angrily, "But who gave you this mission, Yasha? I don't like this. How do we even know that we can trust that person? This could be some HYDRA thing, couldn't it?"
"Krasotka, if I cannot trust the person who gave me the mission, then I cannot trust anyone. That's all I'm saying. This ain't HYDRA and it is something I gotta do. I'm just relieved as f*** to be finally letting this responsibility go."
Thea stared at Bucky for quite some time before she said gasped and exclaimed with shock, "No! Steve wouldn't do that do you, Yasha. I don't believe it."
Baring his teeth briefly in a feral expression of intense frustration, Bucky snarled, "HE DID. I was there."
"But he had no right to give you a mission back then, Yasha! You were not stable yet. Besides that, you told me that you hadn't had any contact with Steve since you pulled him out of the Potomac until that day in Bucharest."
Bucky punched the bedroom wall enough that a network of cracks spread across the wall and some of the plaster rained onto the gleaming hardwood floor. "Why are you pushing me on this, Thea? This is not something that you want or need to know."
"Because, Yasha, our relationship was built on what happened during that time. I trusted you to keep me safe even though you were clearly barely sane. I followed you even when you hardly seemed less dangerous than HYDRA, since I believed in you. You were not very nice, but you appeared sincere and genuinely determined to protect me. If you lied to me about not having talked to Steve, then what else did you lie to me about?"
Bucky closed his eyes and rasped miserably, "Bella, no. No. I didn't lie to you. It wasn't Steve. Not my Steve. It was another Steve. S***. Well, it was my Steve, but from the future. And yes, I know how insane that sounds, but it is true. So, I hadn't spoken to my Steve. I didn't lie to you. And…I don't know how to explain it to you. The Future Steve gave me the mission, but it wasn't…s***. He gave the mission to the Winter Soldier, not Bucky."
Thea stepped back as she gasped in horror. "He used The Words?"
Using his vibranium arm, Bucky briefly pulled her into him and kissed the top of her head lovingly. Then he released her so he could look down into her face as he replied in a hoarse, despondent voice, "Yeah. Yeah, he did."
"I cannot believe that Steve would do that! That is…it is unforgivable."
Seeing the shock and anger on Thea's face, Bucky shook his head and grunted as he tried to figure out how to explain. He couldn't have her start distrusting or disapproving of Steve because of all this. "Well, it would be if Future Steve didn't have permission, but technically he did, krasotka. Apparently, Future Bucky gave him permission and even came up with the plan."
He dropped his head back onto the wall with a loud thud, causing a further chunk of the wall to crumble onto the floor, and continued furiously, "Frankly, Future Bucky can suck it, but apparently that future was very different than our time. Somehow, I didn't have a family in that future, so I volunteered myself to do the mission, as I had the least to lose of anyone we knew and the skill set to get it done. Xavier thinks that when Future Steve time travelled, he created a separate timeline that we are now living in. I don't know, maybe he did. But regardless, I still got this mission and, since it's a Winter Soldier mission, it is going to eat away at my brain until it is completed."
Thea stood far enough back from Bucky that she was outside his arm span, as she placed both hands on her hips and demanded, "Hold on a moment. So…some Future Bucky gave a Future Steve permission to come back and activate the Winter Solider to complete a bizarre, secret mission on which the fate of half the world depends? And you believed all this because some purported Future Steve said so? And this all occurred at a time before you met me when you were so unstable that you still didn't know past from present? And Future Steve thought that, despite being just barely escaped from HYDRA, you were the best choice for this all-important mission? He didn't think that there was another time period that was, perhaps, more advisable to come and force this on you?"
Bucky nodded. "That is pretty much exactly right. I didn't ask for details then, since I was the Winter Soldier. When I was owned by HYDRA—especially the Soviet branch—questions were not permitted unless I was asking for mission critical detail or supplies. Sometimes I was punished even for that. Future Steve didn't give the Winter Soldier permission to speak, so I didn't. Future Bucky probably told him not to, but there are so many details that I wasn't given that would have been immensely useful in carrying out this d*** mission."
"I cannot imagine Steve, any Steve, doing this to you, Yasha."
"There must have been a very good reason. There has to have been, Bella. There must also have been an unavoidable, galaxy-destroyingly horrible outcome if Steve tried to do the mission himself and it would have had to be so clear, inescapable, and horrible to make it obvious to my stubborn, self-sacrificing pal: Captain I-Love-Danger. Nothing else would have gotten him to agree both to have me do it and to activate the Soldier."
"I suppose."
Bucky dropped into the large, leather club chair beside the window and said desperately, "No, I know Steve, Thea. I know him. Back when Future Steve activated the Soldier, it tore to shreds all of the parts of me that had begun to hope that I could find Steve and he would help me. I'd already been to the Smithsonian in an attempt to make sure that what I thought I remembered really was true. I saw the exhibit and I watched that video. I saw how Past Bucky smiled as I looked at Past Steve and how I then laughed. At that point, I couldn't actually remember EVER having laughed. I didn't remember joy. Seeing someone with my face being capable of that emotion was…I can't explain."
Bucky hid his face in his hands as he hunched over in the chair. "But that guy—Past Bucky—trusted Past Steve like all my instincts said to trust any Steve anywhere in any time. And that guy, Bella, was me before HYDRA f***ed around with my brain, but after they'd injected me with the serum at Azzano. I was already changing then. I was living in a half-shadow h*ll at that time but I could still believe in Steve—who looked so different from the way I'd always known him—yet, who was still completely Steve Rogers, my brother and friend. I trusted him then. So, I trusted Future Steve even when he activated me despite the fact that it nearly destroyed my capacity for any hope that I could ever be Bucky Barnes again and not the f***ing Winter Soldier. Regardless, you gotta know that I trust my Steve now and I do trust what Future Steve said. We aren't going to question that anymore, Thea. Understand?"
She flushed and said quietly, "Ok."
"I won't pretend that I wasn't angry when it was Steve's voice that said The Words and his face that I was watching as the Winter Soldier received mission orders. The Winter Soldier didn't know why he knew Steve, but he was furious. He knew that everything was wrong with the man who was somehow both a former mission target and a recent ally suddenly acting as a handler. He actually didn't want to accept the orders at first. Once I'd come out of the Soldier fugue and I was Bucky again…I got so violently ill that I was tossing up blood. Everything I had started to believe just dissolved and I couldn't think. So, I ran until I had to fight two supposed SHIELD goons who wanted to take me in, but I wasn't about to go with anyone with that tattoo behind their ear."
"Oh Yasha. You must have been so scared."
Bucky shrugged. "Honestly, I was barely lucid, krasotka. Then, when I saw you standing there looking up in terror at me as I was pressing you against the wall, my sanity and my ability to process my memories were utterly derailed because suddenly ALL I wanted was to stay near you and protect you from everything. Nothing else mattered, especially not Future Steve's mission. But the Winter Soldier in my brain didn't let me ignore it, so I was sunk so deep in h*ll at that time that I have no idea how I managed to function enough to get us to Alaska. Furthermore, I was struggling to get clarity on what Future Steve had actually said versus memories from my past of my Steve that somehow kept getting caught up in the mess. I did finally get all that worked out, but it took a long time. Months after I'd met you."
"That explains a lot of what happened back then, Yasha."
"I suppose. But I would always have been a disaster if I'd met you then, Bella. The secret mission from h*ll was just sludge icing on a s*** flavoured cake."
"So, you are absolutely certain that this mission is legitimate? You're positive that it is real and not something HYDRA made you believe?"
Bucky pulled Thea down into his lap and wrapped her in his arms. He buried his face in her hair and breathed in and out deeply for several minutes before he replied hoarsely, "Well, I was mostly sure, Bella, but then Xavier confirmed it. So, it did happen: Future Steve crying when he said The Words in a truly terrible American accent, being given a mission with terrifying ramifications if I failed, the Winter Soldier raging with anger that he was being forced into service again and without any support and too little information, Future Steve apologising four different times before he returned to his time or whatever the h*ll he did, waking up in an alley with two broken ribs, a broken toe, and a concussion next to two dead bodies with HYDRA tattoos. All of it was real."
"Oh Yasha. I am so sorry you went through that. I am so sorry."
He held her for a while and then breathed out with audible anguish. "Apparently, I have Future Me to blame for this whole ridiculous plan. My Steve has nothing to do with it, Bella, so please don't blame him."
"I won't. I understand. The Steve I know would never say The Words. Something horrifying must have happened if any version of Steve would even consider this plan."
"I have not told Steve about any of this yet. Once I'm back from Westchester, then I will explain to him and to Mary-Claire. All four of us will know that the box was hidden, yet none of us will know where it is. The person who wants it…honestly, Future Steve only told me about one but I can think of a lot of people who would want something like this…well, the person who is looking for it won't care whether I've told you or not. You are at no more risk knowing that I have had this object than if you hadn't known. He'd torture and kill you either way. So, you might as well know so you can be careful."
Terrified, Thea breathed out shakily and peeked over at connecting door to the room where her son and daughter were sleeping. "Is…is that likely?"
"No."
"Oh. OK. But what is it, Yasha?"
Bucky's voice changed as he sharply warned, "No, you don't need to know that. Ask me no questions about that. Did you ever open the box?"
Thea shrugged and then turned towards the very large painting that was hung above the bed, as she replied coldly, "No. I just saw the weird symbol on the top."
"Even if you had, what you would have seen was not real. Future Steve told me that the object had some magical thing done to it, so it would not appear to be what it truly is to nearly anyone who looks at it."
She scoffed, "Magic."
"Yup. Also, it was an alien who transformed it, but another alien who is searching for it."
Thea cut her eyes over to him and said warningly, "Yasha."
Bucky responded roughly, "And yet another alien was the one that made it in the first place. Yeah, I know this is all nuts, Thea, but I am wearing a f***in' metal arm that is vastly stronger and just as flexible as a real one. I was born in 1917 and here we are a century later, yet I'm still in my 30s physically. Steve and I can both leap from one building to another and run faster than a car. Aliens attacked New York on a flying dragon ship. I fought Steve on an invisible flying aircraft carrier. Honestly, it isn't as hard to believe Future Steve's story as it should be."
Flushed bright red, Thea quietly answered, "Well…I suppose that is true."
Now almost snarling, Bucky continued, "So, whether you believe it or not, I do. I'm gonna complete my mission and then, hopefully, finally be at peace about it."
"Ok, Yasha."
"Ok?"
Not lifting her eyes to his face, Thea sighed. Then she lowered her voice even further, as she explained, "I don't like any of this, but I trust you so I'm going to choose to accept it."
"Ok. Good. Thank you, krasotka."
After several moments of silence, Thea asked suddenly, "Yasha, exactly how long before you came to my flat did you see Future Steve?"
"Πолный пиздец! Why do you need to know that, Thea?"
"Yasha, please answer the question."
He looked at her for a moment and then sighed. "It was almost nineteen hours."
"Nineteen hours? Yasha! That's…that's why you barged into my flat, isn't it? And why you were so rough despite it being weeks after the fight on the helicarrier. Your personality was only just coming back from being reactivated as the Soldat."
"Yes."
"Oh, Yasha. Were you already becoming more yourself before Future Steve came and used The Words? Did he take that away from you, too?"
Bucky slumped back onto the chair again and grunted miserably. "It doesn't matter. This was a mission that someone had to do, Thea. I understand why I was selected. They obviously didn't know that I'd find you."
"But I still cannot believe that Future Steve couldn't have come back and task his past self with the job. What could have been so terrible that torturing you with this was preferable?"
"I don't know, Bella. I have wondered that so many d*** times. It is incredibly unlike Steve to agree to this plan. I don't understand at all. I don't…but…anyway, it doesn't matter. I was chosen and, apparently, I actually volunteered myself. And, the way I see it, baby, this s*** mission is probably the only reason that I met you. So, in a way, I should be f***ing grateful as h*ll for it."
"I don't understand that, Yasha. Why?"
He scrubbed both hands aggressively through his thick, unruly beard and said gruffly, "I had a place that I'd been sleeping and hiding out for two weeks before Future Steve came. I was planning to stay there for at least another week while I gathered intel and supplies. Since Future Bucky had apparently told Future Steve where that was, I began worrying who else might know or if HYDRA might find me. So, I had to get away and do something unexpected and out of character. That's what led me to your door that day. Future Bucky never did that, so he never met you. This f***ing mission gave me you and the babies."
"Oh. Well…I still think it was horrible of Future Steve to do it. But I'm immeasurably glad that you chose my door that evening, Yasha. I love you so much."
"This is why Xavier believes that we are in a separate timeline, krasotka. If Future Bucky is the same person that I am, he would have allowed the entire universe to burn before he gave you up. Therefore, I assure you that there is no chance that Future Bucky had you. Honestly, I probably would never have left Wakanda if I had not needed to save you. Not unless Steve was in danger or something. But the fact is, we're here. I have this mission. I gotta get it done and tomorrow is the day."
"Ok, Yasha. I understand. Whatever it is that you need me to do, I'll do it. Just explain to me the plan for tomorrow, ok?"
Note: Tetya means Aunt, whereas Dyadya means Uncle. Styopa is a very common diminutive for Stepan (the Russian form of Steven).
Just as a fun aside: Check out 'Dyadya Styopa'. They were a series of poems by Sergey Mikhalkov, which was written about an enormously tall, strong, noble, and heroic policeman (Stepan Stepanov, i.e. Dyadya Styopa) who saves the day in over-the-top ways. The poems were written for children (specifically those in the Komsomol) during the early Soviet period, but were used for decades.
This is just the type of snide cultural reference that Natasha would make to Bucky (the likes of which only they would find amusing in the aftermath of their common horrifying Soviet-era experience), who would find the parallels with Steve to be quite hilarious. After which, of course, Bucky would insist that his children would have to call Steve 'Dyadya Styopa'. Steve, on the other hand, thinks that Bucky needs to find a better sense of humour and is looking forwards to when his twins can return the favour with Uncle Jimmy-the nickname that annoyed Bucky most during childhood. Natasha, to be honest, is quite amused by the surprising childishness of the world's two most powerful supersoldiers and (with Sam) finds them to be a source of continuing entertainment.
