It was easy meeting Doctor Bruce Banner. He knew he was sensitive to the Hulk, and so he made damn sure to help him feel comfortable around him. He was Captain America, and his team needed to trust him and be at ease with him. Even if Bruce was here just as a scientist, he was still part of the team, and the moment he’d seen him on the flight deck, he knew immediately what he was going to say.
It was as far from easy as possible, bordering on psychotic and dangerous, meeting Tony Stark. He’d been terrified of the sudden metal man that dropped out of the sky followed by the noisy, angry rock n roll blasting out of the jet, and, when he’d finally gotten his marbles together to understand who he was, he was more nervous than anything. This was Howard Stark’s son, one of his closest friends, a man who had been searching for him until his own death, and this was his son. And then Tony had let the helmet close in on itself, and Steve nearly choked. He called him Howard that first time on accident, and he and Tony have been on different pages ever since.
When he walks in the lab, however, and sees Tony jabbing Bruce with some pointy metal thing, he knows, more solidly than he had after that first conversation, that it’s going to be very easy to separate Tony from his father. He’s nothing like Howard, and it makes Steve sad. When he’d first heard the name Stark, he’d actually felt a little lighter, felt like he could finally find a friend, someone he half-knew, if only by their parentage, and then Tony had tossed that all out. And now here he is, trying to antagonize Bruce into Hulking out. He really and truly hates bullies.
He snaps some words at Tony, and he’s mostly paying attention but for the little smirk that turns the corners of Bruce’s mouth up at their interaction, and, when he’s left, he looks back through the small window pane on the door and sees Tony roll his eyes and Bruce laugh. He doesn’t understand, and so he goes to investigate whatever Nick Fury’s up to.
Later, when they’re all gathered in Manhattan and fighting the Chitauri, Tony asks him to keep him updated on Bruce, and Steve frowns. He just doesn’t get it, doesn’t understand what is going on between them, can’t grasp why there seems to be a friendship when Tony is nothing but rude and cruel to Bruce. But then he’s giving the orders, and Tony makes some remark that he doesn’t understand, winks at Hulk before he grabs Clint, and Hulk smiles.
In fact, Steve doesn’t understand it until he’s stopping by with Clint to see what’s up, and they’re let into the lab in the top floors of Stark Industries. Tony and Bruce are going back and forth, talking a mile a minute, and they each barely spare a hand wave to acknowledge their guests, and it’s not even like they’re working. Well, Tony is, but Bruce is just lounging in one of this spinning chairs, legs kicked up on one of the many desks, and telling a story from his time in India. Steve understands when he sees this, when he sees the way Bruce is sitting, so relaxed and at ease, not hunched over and hands always fidgeting like he was at base, when he sees the way Tony just is, so open and genuinely happy, whether he’s laughing at something Bruce is saying or smirking while he solders. It’s maddening, if Steve is honest. Because he just can’t understand their friendship, even though he knows it’s there.
They get an emergency call to Stark Tower two months later saying that Hulk has made an appearance, and they ride the elevator down into the basement. When they enter the workout room, it’s through the shattered glass of the doorway, and someone is laughing. It’s a loud, deep rumble, though, and Steve realizes, almost belatedly, that it’s Hulk. The noise of a repulsor sounds, and then Tony comes into view, in full armor, careening through the air before he finds his balance and halts midair, hands and feet alit with energy. He shoots back out of their sight, and Hulk roars loudly before the walls shake and Tony’s voice whoops through the air, cheering.
“Alright, big guy, I’m done,” Tony says, and they finally get far enough in that they can see everything. Hulk is sprawled out on the ground, picking himself up, and Tony is a few yards away, heading for a side door.
“America?” Hulk says suddenly, and Tony stops, turning.
“Uh,” he manages, and that in itself is a shock.
“What is going on?” Steve snaps, and Hulk frowns.
“America,” he says again, though he sounds put out this time.
“Just ignore him,” Tony directs toward Hulk before shifting his gaze back to Steve, “Just stay there. I’ll be back in a second. Hey,” he adds, and Hulk looks over at him, “Be good, or I’ll throw a weight at your head again.” Hulk shows him his teeth in a frightening growl, and Tony just laughs at him and disappears, leaving the Hulk to sit down and look at the ceiling.
By the time Tony returns, Hulk has shrunk down, and Bruce is getting to his feet unsteadily, a pair of purple pants sagging around his hips. “They worked!” Tony exclaims, and Bruce flaps a hand at him. To the gathered team, he says, “Bruce and I invented pants that shrink and expand, to fit both him and the Hulk. Look, stop glaring at me. We were sparring. It was his idea, actually.”
“Don’t even think about putting this on me,” Bruce grumbles, padding over to him, “You wanted to see if you could make him complacent.”
“He laughed at me. I think that’s pretty damn complacent, don’t you?’
“Whatever,” Bruce says, but he’s grinning, and then, to Clint and Natasha’s amusement and Steve’s bewilderment, he steals a kiss from Tony and then disappears through the same side door. Tony’s blank-faced for a moment before he turns to him, glaring.
“Go home,” he says, and then he’s gone, following Bruce.
They don’t really have any choice but to obey, and it’s not until another month has passed, and they’re actually being friendly, hanging out together with pizza and beer that Steve finally, and truly, understands.
Tony and Bruce have commandeered a sofa for themselves, and Tony sits with his back pressed against the arm, one leg kicked up along the back of the sofa and the other bent at the knee, bare foot resting lazily on the ground. Beneath his legs is Bruce, reclined on his back against Tony’s chest, not really paying attention to them but more to the slow drag of Tony’s fingers in his curly black hair, occasionally massaging his skull, and, even just observing, it’s obvious Tony doesn’t really know he’s doing it, though it doesn’t look like he’d cared if he did. And Steve looks at them, takes in how different Bruce is from that first time he shook hands with him, how far removed he is from that shaky, nervous, closed-off scientist, to now. It’s incredible, and, when Steve flicks his gaze up to Tony’s, who is currently arguing with Clint, he sees it there, too, and he gets it. Tony was never bullying Bruce. He was helping him, always, because he cared about him, saw the scientist and the man, saw the monster but saw it only in that he wanted to help him learn how to control it, and it’s so obvious to Steve where it’s so obvious that both of them are painfully oblivious to the fact that they need each other, that they are so in love. And Steve just smiles to himself a little for having figured it out.