A/N: When I first played through the Hot Spring Scramble DLC and read Lucina's and the Avatar's conversation my first thought was "MARRY HER" and so I set off to write down this exact scenario.
It's already stated in the summary, but just in case someone misread: This is a female Robin/Lucina fanfiction.

Things the reader should know before starting to read:
I headcanon the future children would stay for an extended amount of time with their parents after the game's final chapter before setting off on their journeys, as described by the ending. It is also not stated when the Avatar reappeared on that field after the "sacrifice yourself" end. I won't mention anything either, since it could have been anything between a couple of days and years. Just know that this story follows the sacrifice yourself end and that the kids haven't left yet. I leave it up to the reader to imagine how much time has passed.

The pairings for the future children's parents are based on my safe file. I will avoid mentioning them if I can so that everyone can imagine them to their liking, but there are two that will be made mention of: Chrom/Sumia and Lissa/Libra.

Other than that: Enjoy yourself!

Proposal

Lucina stood at the side of her crib and watched her infant self with gentle blue eyes.

Before she came to the past, she had barely been able to remember how her nursery had looked like and it felt strange being inside the room, even though she had visited it more than just a couple of times after the battle with Grima.

The day came to an end. Orange light shimmered through the window as the sun slowly set on the far off horizon.

Carefully, Lucina stretched her hand out and bent over the crib's latticework to caress her younger self's hair. Oh, how peaceful she slept and Lucina wouldn't have it any other way. The war was over and Grima dead. The babe would grow up without the horrors of war and most importantly with both her parents at her side. She and many other children wouldn't have to experience what it meant to get their parents taken away early by the cruel hand of death.

"Yours will be a happy future." She whispered and her heart was filled with happiness and melancholy alike. Right before touching baby Lucina's hair she hesitated, as the child seemed so content she was afraid to wake her up.

"This is farewell." Lucina said softly, tears forming in her eyes and very gently touched the baby's head with her fingers. It was such a strange feeling, to know that this child would grow up to a slightly different version than the woman she was now. They were the same and yet not.

Part of her was envious that she couldn't have the life her present self would have, that she couldn't enjoy staying with her family that she had longed so many times to meet again during the lonely nights in between battles in the future.

But it was better that way. She had vowed to change the future and that was what she had done. Her goal had been attained, her mission completed. There was nothing left for her to do here. Lingering in the castle for an extended period of time would raise questions and cause only more problems down the road.

Lucina took a deep breath and let go of the baby. She cast a last glance out of the window and got lost for a moment in the rose colored clouds and the changing color of the sky.

When she felt ready to leave, she turned around and froze when she saw a familiar figure standing in front of the door.

"Robin." Lucina had been so lost in her thoughts and emotions that she didn't notice how the tactician had entered the room.

Robin met her gaze silently, her brown eyes ever so steady and calculating; a gaze Lucina had come to know whenever the other woman had weighed their chances in battle.

"Why are you here?" Lucina asked. This wasn't exactly what she had wondered, however. Her actual question was how Robin had known that she would be here, at this hour, on this particular day. But Lucina feared that she already knew that.

"Because your last goodbye had felt too much like a farewell." Robin answered.

Her gaze wandered to the baby inside the crib and then back to Lucina, who had grown tense. "Why do you want to leave?" She asked and the tone of her voice indicated that she knew exactly what Lucina had been about to do.

A small twitch of her fingers gave away Lucina's uneasiness towards the question.
"I've told you long before, didn't I? I do not belong in this time. A woman clinging to the Exalt's side, but who is neither wife nor daughter? The people would grow suspicious. My family wouldn't be able to live in peace."

Of course Robin remembered. How could she ever forget those words exchanged amidst steam and stone?

"There is no guarantee that I'll be able to return to the future once peace is won. If I'm to live out my days in this era, I can't allow myself to linger at my father's side. It would only raise questions. Cause confusion... No, it's best I lived in shadow."

"And I told you that I would think of something. Chrom and Sumia want you to stay here – and I do too."

"I'll fix it. Somehow. I'll think of something. Some way that you can stay with Chrom without arousing any strange suspicion. What better test of a tactician's skill than concocting a plan to convince a nation?" For Robin it was as if she had spoken those words just yesterday.

Lucina frowned. "I know, but…"

"Why do you so desperately seek to live in the shadows of this world?" Robin asked sternly, her hands clenched underneath the long sleeves of her black coat.

"I don't. I just believe it's for the better if I don't stay here."

"The heck you do!" Robin suddenly shouted.

Lucina startled and they both heard the babe stir in her sleep.

Robin lowered her voice when she continued: "Don't try to play the martyr, Lucina. You are allowed to stay here and be by your parent's side. You helped save this very world – your world. It's not some alternate dimension where things went entirely differently and where you may even have had another mother. This child…" She pointed at the cradle. "…would have grown up to be the very person standing right in front of me, if you hadn't traveled back in time to fight against the fell dragon himself."

"But don't you see that this is the problem? There can't be two of us."

"Says who? If you two weren't supposed to exist at the same time, then why would it even be possible to time travel in the first place?" Robin's gaze softened now, her voice only a whisper. "You wanted to see them again… saved their lives… You went through unimaginable pain and fear and lived. And against the odds we achieved the impossible… You deserve to be here."

Her last sentence was merely an aspiration, yet Lucina heard every word clearly. Her expression was stoic, her lips pressed together as a thin line. Her heart started beating faster. Robin's words made her happy, but also caused a lot of conflict inside her.
There was a pain in her heart, from years back when her parents had died. She had thought it impossible to ever see them again and even when she did so in the past, as their younger selves, she had still always had the feeling that there had to be a secret prize to be paid. Staying here in a peaceful time and catch up on what she had lost? It had to be too good to be true. Surely, something horrible was bound to happen if she stayed.

"I will just cause you grief." The blue haired princess replied with a heavy heart.

Robin shook her head. "You believe everything to be too good to be true, don't you?" When Lucina winced, as if she had just read her mind, Robin knew that she was right.

"Even if I didn't, there would still be the problem of me being an outsider." Lucina averted her gaze. Her resolution to leave had weakened. It would be difficult to pursue her initial plan if she continued to further look into Robin's eyes.

There was a moment of silence.

Robin inhaled deeply. She straightened her posture and raised her head confidently. She spoke the next words loud and clearly, in a tone so serious that Lucina only knew it from their times on the battlefield:

"Marry me."

Lucina was caught off-guard. The request echoed three times in her mind before she realized what Robin had actually said. She felt her face grow warm.

"What?"

"Think about it: I'm Chrom's chief advisor and his right hand – and I live in the palace since I had nowhere to return to. If you were to be my wife, then it wouldn't be strange for you at all to wander about the castle grounds or see him on a regular basis." Robin explained matter-of-factly. Her cheeks had turned red, but nothing else in her voice and posture hinted on any kind of embarrassment she may have felt.

Lucina was speechless. The thought of marriage had thrown her out of balance. Her mind was in disarray for more than one reason now.
"How can you… I-isn't there anyone else you'd rather marry?" She asked and dared to look at the other woman again.

"It would be a marriage of convenience. You wouldn't need to follow any of the… marital duties." Robin explained. Despite having asked for Lucina's hand in marriage in a rather bold manner a few moments ago, she had now her gaze averted to the side. "And should you find someone you really love later on then you could just leave me. I wouldn't object."

A heavy breath escaped Lucina's lips. That sure was a lot to take in.

"What do you say?" Robin inquired.

"Gods, this is… madness." Disbelief reflected on her gaze. "Robin, are you sure you want to go to the lengths of doing that?" She needed to make sure.

This plan was crazy, just crazy. But the worst part was that it actually sounded like it could work out.

Robin made a few steps forward until she stood right in front of her. "Lucina…" She took the princess's hands in hers and squeezed them tightly. "I don't know anyone else who deserves happiness more than you do." She answered, this time looking directly into Lucina's eyes again.

Her gaze was sincere. Robin's mind was made up, that was for sure. She cared so much about her, Lucina realized, that she couldn't help but chuckle upon hearing these words. "Why, Robin, that almost sounds like a confession of love."

Uneasiness showed on the other woman's face for a split second.
"It may as well be." Robin said and let go of her hands and made a step back. "Lucina, I'll be honest: I have very deep feelings for you, but I still haven't figured out of what nature they are. Is it deep friendship or love? I don't know." She confessed.

The smile faded from Lucina's face. Instead a faint blush showed on her cheeks. "That's why you wouldn't mind marrying me…" She murmured.

"Please, I ask of you to seriously consider everything I have said." Robin requested. "I will give you some time to think about it. Just… don't leave without giving me a proper answer." She was back at the door now, her right hand on the handle. "Can you promise me at least that?"

Lucina, still taken aback, could barely raise her voice. Instead she nodded.

Lucina didn't leave her room after that. Her mind and heart had been racing, as she recalled everything that Robin had said to her.

Don't play the martyr – was it true? Was she so desperate to cling onto unhappiness? She found it hard to believe that she deserved to stay without consequences. But maybe it was the harsh future that had shaped her that spoke those doubts. Maybe Robin was right and they could figure this out.

And maybe…Robin was in love with her?

She felt herself grow nervous at the thought again. This was not making anything easier. Even if the plan would succeed and Lucina agreed to marry her, what would happen further down the road? Would Robin really be okay with it, if Lucina decided to leave someday with someone else? Wouldn't it break her heart? Could she really take responsibility for that?

As it was typical for her, the tactician had given her an awful lot to think about. Lucina groaned.

Lucina pondered over those and many other questions, without noticing that night had long fallen upon Ylisstol. She had sat down next to her crib now, still thinking, absent-mindedly looking at the spot on the ground that was illuminated by the moonlight that fell through the window.

Eventually she heard someone open the door very carefully and looked up to see her mother entering. She was wearing her night gown and looked very sleepy.

"Lucina." Sumia's lips formed a soft smile when she noticed her grown-up daughter in the dark. "I'm so glad to see you. I feared you were long gone by now." She whispered.

Lucina looked up, needing a moment to recognize her in her daze.
"Mother…" She quickly averted her gaze again. "Why did you think I would be gone?" So Robin hadn't been the only one who noticed?

Sumia stepped towards the cradle to see if her baby was sleeping well, while she remembered the last time she had seen her grown up daughter today: She had seen shadows of sadness in Lucina's eyes while she had said her goodbyes for the day to them. Lucina would always hug her parents after that, but this time the embrace had been a bit tighter than usual, a fleeting moment too long in which Lucina had lingered in her mother's warmth as if she had wanted to take a piece of her mother with her.

"I had a feeling." She answered while stroking her infant daughter.

"Had I been so obvious?"

"Lucina, dear, I'm your mother. I will always notice when something is off." Sumia gently reprimanded her and let go of the baby. She knelt down afterwards, to meet that very daughter on eye level. "So, what is wrong? You seem troubled."

"Mother, I…" Lucina didn't know where to start. Should she tell her about Robin's proposal? Ask her if it was really alright to stay? If she loved her as much as her infant daughter that she would actually see growing up into a fine woman?
But she knew Sumia's answers to those questions already: Do what will make you happy, yes and of course I do. It was pointless to ask the same thing over and over again. She needed to figure this out on her own anyway. After all she would have to live with whatever decision she'd make.

"Mother, what would you think about a marriage between two women?"

Sumia stared at her with wide brown eyes. From all the questions she would have expected to come out of her daughter's mouth this had definitely been not one of them.

"I – I'm not sure. Are you asking if that's possible? If so, then it would be best to consult Libra." She answered abashed. "Why, i-is there someone on your mind? Know that I'd love you no matter what!"

Lucina blushed, not sure what she had expected. The unconditional support of her mother made her happy every time anew, but she hadn't intended to ask because of that.

"Don't you think it's weird?"

Sumia furrowed her brows as she thought about it again. "Why? I think a woman can love another woman just the same as a man could. To be honest, I love the idea of love being so strong that it transcends gender." She smiled bashfully. "And… to tell the truth, I had a crush on Cordelia in my early teen years."

Lucina stared surprised at her mother's face, who in turn offered an encouraging and warm smile. She hadn't known about this side of her mother, but the fact that she had opened up to her about something like that made her feel very special.
She was so glad that they were able to talk about these kinds of things and happier yet, that this was another mother-daughter experience she was able to share with her.

Her heart filled with joy and she realized that she didn't want those moments to end. She wanted to make more experiences with her family, get to know them even better and collect happy memories outside of battle and war – things she had thought to be impossible for the longest while.

She had told herself long ago that she would be content with the memories she had already made, with the second chance that Naga had given her when she had sent her back in time, but now she realized that she didn't want those things to ever end.

Was it selfish to think like that?

Everyone had been telling her that she deserved to be here, that it was okay and she had not believed it to be this easy.

But maybe, just maybe this once things were just like they seemed.

"Lucina, dear? Why are you crying?" Sumia suddenly asked.

The question snapped her out of her thoughts. "Crying?" She touched her right cheek and indeed, tears had started to stream down her face. Lucina tried to smile, the tears falling even more now.

"I-it's nothing…" Her voice was stifled. "I'm… I'm just happy – it's alright to be after all, isn't it?" She asked while trying with moderate success to wipe the tears away with both hands.

"Oh, Lucina…" Seeing her grown up daughter like that brought Sumia on the verge of tears too. Lucina had been so strong all the time and still so desperately tried to be, it pained Sumia to see her struggle like that. She leaned forward, wrapping her daughter in a tight embrace.

"Of course you are, dear. Of course you are." She assured her and felt how her daughter held on even tighter than the last time they had hugged.

Lucina burrowed her head in her mother's shoulder and started to sob.

Robin was leaning over the handrail of her room's balcony and watched the people of the town go about their busy morning routines. Some were grocery shopping at the market, while others were diligently pursuing their craft. She saw mothers with their children, older kids running through the streets playing tag and merchants trying to sell their goods.

It was uplifting to see the people they had saved enjoying their lives and to catch a glimpse of those ordinary everyday moments. She rather saw children fall down and scrap their knees and getting reprimanded by their mothers for running too fast, instead of bending over their dead parents' bloodied bodies and crying out a different kind of pain.

She tried to watch out for Chrom, knowing that he would visit the market soon to blend in with the people, as had his older sister done during her reign.

Robin inhaled deeply. Oh, how much she enjoyed the fresh morning wind. It was as if it brought the promise of a wonderful new day.

"Robin, may I have a word with you?" Someone behind her asked.

She turned her head around to meet Lucina with a small smile. Robin immediately knew that the woman behind her had made a final decision. The air around Lucina seemed to have changed, but Robin felt that it was a good change.

"You may."

Lucina nodded and took the place on the handrail next to her. Watching the people go on about their lives from far above gave her a sense of accomplishment. It was so different than seeing the streets crawl with Risen and dead.

"I wish to live a happy life." She said, her eyes following the trail of people in the distance.

"I wish the same." Robin responded and turned her head towards the direction of the market again.

"If I left, I don't think I would ever stop thinking about how things could have been." Lucina inhaled deeply. "I'm happy when I'm with my family; happy to talk to mother and father and be able to have them around me and guide me." She paused, taking the time to think about the talks she had had with Robin and her mother just yesterday. "I think I spent too much time telling myself that second chances didn't exist and that this world wasn't for me." She finally confessed.

Robin listened intently, while pretending to still watch the people. She had a feeling she knew where this was going, but tried to stay calm.

Suddenly, Lucina's left hand was on her right.

"Robin… you are a very dear friend to me. Being able to meet you was one of the greatest gifts this era has bestowed me with." She squeezed her hand a little. "Your well-being is as important to me as mine is to you, that's why I will have to ask you again: Would it really be alright for you if we married, just for the sake of me being able to live in Ylisstol castle?"

In response to Lucina's hand squeeze Robin intertwined their fingers and held her hand gently, but also firmly. She had thought a lot about her plan to help Lucina stay, ever since they had talked about it during their visit in the hot springs.

Marriage had been the first thing that had come to her mind, but she hadn't taken it seriously and had put it aside with a chuckle. But time and time again she had found herself developing the idea further and when she realized for the first time that this could work out, she had been in for some serious soul-searching. Why had that been her first thought in the first place?

She had tried to observe her feelings and actions towards Lucina, to figure out how she really felt for her, but to no avail. The only thing Robin knew was that she wouldn't mind, should she have to spend the rest of her life with her.

"Yes." She answered resolutely.

"In that case…" Lucina turned around to face her and smiled. "I accept your proposal."

A/N: I hope you enjoyed it. This is the first part of the deal, next follow two chapters with arrangements (how will Chrom and Lissa react to the news? What about rings etc.) and the last part will be the wedding itself.

I just really love this ship but I haven't been able to find much fanfiction about them. Be the change you want to see, I guess, haha. I have a couple more stories with them on my hard drive but I don't feel comfortable uploading them yet. But if anyone is interested I will gladly do so.

Constructive criticism and other opinions are greatly welcomed :)