A/N: I should be studying… but I'm not, as you can tell. This is not much of anything, really. I feel like it's terribly out of character. I plead ignorance, having only seen the Iron Man movies and the Avengers. I tried to plan it, but it exploded in ways I didn't expect.

Five times Natasha and Steve were siblings to each other

one
It's not so long after the whole mess with the Chitauri that the Avengers are once more required to assemble.

There are explosions every which way, but luckily this time it's a pretty much deserted area in the middle of the desert.

Somehow, inexplicably, the Captain is caught unaware by a blast while throwing his shield. He's knocked back by the blast, burns covering his chest and arms.

The other Avengers are busy, caught in their own fights.

Natasha sees him and catches the shield as it heads towards her, where she's supposed to be protecting his back.

Her vision flashes red and she moves to the injured man's side.

When the fight ends, the rest of the Avengers see a scene that they didn't really expect.

Natasha is leaning over Steve, looking confused about what to do.

The amazing thing is that they can see the panic on her face and when she sees them, the desperation.

two
Steve's confused.

He's often so, but a little unsure of who to ask this time.

It's not a technology or science issue, so Bruce and Tony would not be the best people to ask.

He and Clint talk, but not a lot and it might be awkward to ask about these things.

Thor is great, but wouldn't be much help with regards to this.

That leaves Natasha.

He seems to have a curious relationship with her, it's comfortable and he knows that if he asks her, she won't think him strange and that's a nice thought to have.

Decision made, he goes to the training room, then the shooting range without success, before finding her reading on the sofa in the living area.

"Hey," he says, sitting on one of the chairs nearby.

She puts her book down and looks up at him, assessing for the barest of moments before responding.

"You want to talk about something?" she asks, and he starts. How did she know?

She notices that motion, although small, and elaborates. "You're here without anything to do, and your back is to the television."

Steve notices these things as she says them.

"Uh, I just wanted to ask about some words I came across. I was on the internet and used Google to search some books and comics I remember, and several unfamiliar words came up. Here," he slides a list to her.

She pauses to read the list - which contains some fandom terms, from feels to slash and all the way back again - and then laughs and explains to him, without condescension of any kind, what each of them means. He blushes sometimes, but she only smiles.

"Thanks," he says as he makes to leave the room.

"No problem," she says, still smiling, "Any more questions, I'll be happy to help."

three
Natasha and Clint are still technically agents of SHIELD, so they still have their own missions. They're separated this time, and Natasha returns back to the tower earlier than Clint – and in a really bad mood.

Steve is a little wary about approaching her, but someone needs to go talk her out of her locked room.

The others are even more scared of her (she's not that scary, is she?) so it's up to him to do it.

He knocks lightly on the door. There's no response, just like there hasn't been for the ten or so hours she's been home.

"I'm coming in, whether you like it or not. If you open the door, I won't have to break the door down."

He hears a movement, the click of a lock. He pushes the door open, sees the mess that's inside and then looks for Natasha. She's huddled on the bed, looking thoroughly angry and miserable and weary.

He walks inside and takes another look around the room.

It looks like she's been throwing things around, by the sheets strewn across the floor and the slight dents in the walls.

He sits beside her, close but not touching. He knows not to ask, because it's obvious she's not okay, and if she doesn't want to share, well that's okay to him for now as well. He'll just give her his company.

"They were only children," she whispers, knees drawn up to her chest. "They'd done nothing and they still…" she trails off.

"I'm sure you tried your best." There's so much more he should say, but he doesn't know how to phrase it. He doesn't know how to express that he too wished for peace, wished the innocents needn't suffer, that children didn't need to grow up too fast in a way that would do justice to these thoughts.

She jumps up with an angry huff, fists clenched, trembling only slightly. "That he could -" She lapses into Steve thinks is Russian, but is unmistakably angry.

"Spar with me?" Steve asks after a moment. He knows that she usually does it with Clint after a mission and he's not around this time.

"Are you sure?" She sounds hesitant.

"I'll be fine." He smiles, and she does too, although it doesn't really reach her eyes.

She is really angry, he finds as they fight in the ring, but by the end of it, she's relaxed a lot more, even if the haunted look still hasn't completely left her eyes.

"Thanks," she murmurs as they make to leave the ring.

"It's nothing," he responds.

Even though he wakes up a little sore and bruised (which quickly fades, thank to the serum, damn she was angry), he thinks it's totally worth seeing his teammate – family, sister – happier.

She greets him warmly at breakfast and smiles slightly when he sits down next to her. Tony's face at this point is almost comical; Bruce and Pepper kind of get it, but only a little, and even then, not really.

four
Natasha and Steve are sitting in front of the television and playing, of all things, New Super Smash Bros. Brawl, when Tony walks in.

He's a bit surprised at the sight. Actually, that's an understatement – a huge understatement.

Natasha is calmly winning with the grace with which she seems to do everything. Steve, however, is swearing like the solider he is.

Tony would be – appalled? he guesses, but all rational and coherent thought has left him for a moment – if he weren't so surprised to hear the epithets that were coming out of Steve's mouth as he fumbles with the controls.

It's simple to see that Steve isn't great at this. However, he accepts Natasha's suggestion that they team up with a huge grin on his face.

It surprises Tony more than it should to see Steve relaxing like this.

He still doesn't get it.

He knows someone that might.

Tony finds Clint in his room, at his desk, doing a stack of paperwork.

"I'm not disrupting anything, am I?"

"No, I need a disruption." Clint finished the sentence with a flourish and turns to face Tony.

"I was wondering," Tony begins and is unsure how to continue.

"Yes?"

"Do you know why Capsicle and the Russian are such good friends?"

Clint quirks an eyebrow at this. "Why do you need to know?"

"Because. Don't you think it's a little weird that those two hit it off so well?"

"No?" There's a questioning inflection in that statement and Tony wonders if he missed something.

He voices that thought.

"No," Clint says, pauses, and restarts, "Well, yeah, actually, maybe. Natasha needs someone who's serious when needed, but still relaxes with her and understands why she does things. From what I know of the Captain, he feels protective of her, even though she's capable. He doesn't overdo it thought, so she tolerates it."

Tony mulls over that for a second.

"What are you to her then?"

Clint smirks and says, "Wouldn't you like to know," and turns back to his paperwork.

Tony shakes his head and leaves the room, calling "You're sleeping together, aren't you," over his shoulder, needing to have the last word.

Clint doesn't answer, but his smile, hidden from Tony, widens.

five
It's a long while after he initially wakes up in this new world when his life isn't about meeting people and reading up about new cultural values. He finally has some time to himself to do what he wants.

He looks them up.

Everyone he knew is dead and gone. He knows that, but reading about how each of them goes just makes him sadder and sadder. He doesn't give up, though; like a good leader, he wants – needs – to know what happened to his men.

He saves Peggy for last.

Several years after the war, after he crashed, she married, had children.

He is happy for her.

He's just shutting down the computer when Natasha walks in.

She sees the nostalgia on his face mixed with the sadness of loss.

She smiles softly, asks if anything is wrong.

"It's strange that everyone I knew is gone now. I thought I would die with that plane, but I wake up in this new world. I miss them." His smile is bittersweet.

He doesn't need to say anything else. She gets it.

In the silence, he quietly tells her about Peggy: about her strength and her beauty, about how he had loved her.

She listens.

The next day, she hands him a slip of paper. It has an address on it.

"What is this?" he asks.

"Where she is buried."

He doesn't ask who or how; he knows.

Before he leaves the room, he remembers his manners.

"Thank you." After a moment, he adds, "You're welcome to come, if you wish."

She drives him there and enters the graveyard with him, but wanders off as he approaches her gravesite.

She lets him have a private moment with his lost love.

They meet again at the entrance and make their way back to Stark Tower. The ride is silent and if Natasha notices the tears on his face, she doesn't say anything, but hugs him tightly when they get out of the car once they reach the tower.

In return, he holds her tightly, expressing his thanks in the gesture.

Prompt: "[Gen] Natasha, Steve - Friendship/Like Siblings: In the movie, Steve protects Natasha with his shield during a blast. I want more of this! And not just from Steve. I'd love some big sister!Natasha jumping in to protect a hurt Steve during a fight (this, especially this!), and Steve coming to her for advice, and her instinctively going to him when she just needs someone to talk to/be with.
Bonus points for Tony being all o.O over the way Steve magically brings out Natasha's softer side, and Natasha magically brings out Steve's happier/easy-going side.
Extra bonus points for Steve crying on Natasha's shoulder at some point - over Peggy, and Bucky, or missing "his" world in general - and Natasha not being awkward in the slightest about comforting him."