So when Steve comes home one day with an arm full of baby, Tony isn't entirely sure what to do. At first he just sort of stares, because Steve has an arm full of baby, and at a closer glance it's less like baby and more like an arm full of pre-toddler toddler. Tony Stark isn't, has never been, a child type of guy. Children break things. Children wear diapers that they poop in. Children scream, and cry, and make it hard for adults to do anything, anything at all, even when that something is, oh, say, sitting down and relaxing -- yeah, children make that impossible. Which is why Tony isn't sure what to do.
"What... what'cha got there, Steve." Tony gestures to the baby-toddler-burrito that Steve is cradling, and Steve stares at him like he's grown a third head.
"It's a baby, Tony."
And, wow, leave it to Steve to totally be as obvious as the sun in the sky.
"I know that," Tony starts, "but why do you have it? I mean, why is it in your arms?" Then Steve looks down at the thing -- and oh, god no, god, god no. Tony can seriously feel his heart stop beating in his chest (or maybe that's the arc reactor, and maybe he should check that out), because Steve gives that thing a look. And Tony knows that look. It's the same look he remembers Steve giving their first dog. That 'I-know-we-just-got-you-but-i'm-already-really-attached' look.
"He was... just sitting there. In the trash can, Tony. The trash can." Tony loathes the way Steve's voice softens. "I heard something crying, so I went for an inspection, and there he was: all curled up in a ball, shoved in a soggy box." Steve looks up, a fiercely determined line creasing his forehead. "Someone left their child in a box, in a trash can. And that isn't right, nor okay, so I brought him home."
Tony feels like he's going to cry. So what if this kid was in the trash can? He didn't like kids, and he didn't want one, so he opens his mouth to tell Steve to take the thing to a hospital or something, an orphanage, a trash-can-baby relocation camp--
But Steve's facial expression drops from determined and serious to pleading and desperate, and Tony deflates quicker than he'd like to admit. With a resigned sigh, because he realizes this is his fate, Tony mumbles, "I'll go start a bath."
He turns on his heel, all for marching off, but Steve catches him by the arm, the other still curled around the babyrrito. Tony turns his head and Steve is smiling something rich and happy. "Thanks, Tony." He says quietly.
And if Steve is going to smile like that more often, then maybe having this baby thing around won't be so bad.