The heat of it always surprised him. Tony never expected to actually feel the heat, to feel like he was burning up from the inside out. No matter how many times it happened in his life, he always as caught off guard as he had been the first time it happened at seventeen. Locking himself in his room didn't help, cranking the AC until it was frigid did nothing more than make JARVIS warn him about frostbite. It didn't help the aching hunger that rose up from his gut and left him wanting.
"Baby, JARVIS called." Steve's voice was hungry too, but restrained. Tony keened softly, and Steve came around the corner, nostrils flaring as he took a deep whiff. "Baby, you should have called me earlier. JARVIS, bring the temperature up fifteen degrees."
"Of course, Captain Rogers."
Steve had just come from the gym; Tony could smell him even from across the room. His armpits were heavy with pheromones and Tony moaned softly. "I was busy," he managed. "Didn't want to bother you." Steve was a vision in his tight white tank top, and Tony's fingers itched to rip it off.
"You're never a bother." Steve was across the room in a few steps, crowding Tony up against the wall. "Mm... You smell so good, baby." Steve's hands were big and somehow hotter than Tony, burning where they sat on his belly. Tony dropped his head back as Steve buried his nose in his neck. "So good." Steve's nip at his throat left Tony a whimpering mess.
"Steve, please..." Tony's hands scrabbled at Steve's waist, tugging at his shirt until Steve relented and let Tony pull it off. Warm skin met his fingers and Tony pulled him even closer. He was hard already, leaking. He'd never been harder than now, with Steve right in front of him, he was sure. "Steve, I need you to fuck me."
Steve nipped Tony's throat again, sweat salt-tang on his tongue as he soothed the bite. "I'm gonna fuck you, darlin'," he murmured low, Brooklyn accent rolling out thickly as it always did when he got worked up. "I'm gonna fuck you so good..." He ground his hips against Tony's, his own hardness thick against Tony's thigh.
Tony yelped as Steve picked him up a moment later, swinging him up and into his arms, carrying him down the hall. He dropped Tony unceremoniously on the bed, grinning broadly at the older man lying flushed and waiting. "You look gorgeous like this, darlin', just waiting for me." He pulled Tony's sweats down with obvious glee, grinning as Tony gasped and moaned. Cool air hit his leaking cock and Tony shivered.
"Enough waiting, Rogers, and fuck me already!" Tony growled impatiently, hooking one leg around Steve's waist and pulling him closer. In response, Steve pinned him with one arm, claiming a devastating kiss. Tony groaned, but by the time they broke apart, Steve was naked too. His cock stood proudly between his legs, knot slightly swollen. Tony instinctively dropped his legs apart; he knew what would get this moving. "Alpha. Fuck. Me."
Steve didn't need any more invitation than that, kneeling over Tony and sliding in. He groaned at the tight, slick heat his Omega offered. "Tony..." He thrust in small increments, listening to Tony moan. Reaching between them, he wrapped his hand around Tony's cock, stroking it in time with his own thrusts. "Oh god, Tony... you feel so good."
The heat was abating. It always did as soon as Steve was there; Tony didn't know why he'd hesitated. Then he remembered. "Steve... Steve... My pill." He spoke between kisses, groaning softly. "I didn't take my pill."
Steve's thrusting slowed, and he panted for a moment, fighting to clear the heat. "You mean..." His hand shifted, stroking Tony's belly. "You could get pregnant?"
Tony nodded slowly. "Yeah," he murmured, grateful for the reprieve from the heat so he could think clearly. "Yeah, I could."
Steve groaned again. "Do you... want that?"
A nod. Tony wasn't sure he could bring himself to say the word; it was unlikely to happen anyway. He was old, hadn't taken care of his body. Steve grinned anyway, and leaned down for the filthiest kiss Tony thought he'd ever had.
"You're gonna look so good, darlin', all round with my baby." Steve rolled his hips and Tony moaned again. He could feel the start of Steve's knot just beginning to swell. Steve kissed him again and started to thrust. "You're gonna be a picture. Just all filled up... I'm gonna make sure everyone knows that you've got my baby... You're gonna be such a good daddy, Tony..." His mouth wandered, nipping at Tony's throat as he picked up the pace. Tony whimpered, arching up to meet Steve's thrusts. Every word Steve said sent a shot of heat through him and Tony gasped, wrapping his legs around Steve's waist as he felt the knot start to catch.
"You're gonna get so round... So pretty... You're gonna look so good, baby..." Steve's words started to lose focus, getting softer around the edges and Tony groaned, arching a little higher as Steve thrust one last time, knot catching as he came. A few more strokes of his hand and Tony came too, clawing up Steve's back desperately as he did.
Steve rolled them gently to their sides, legs still entwined to keep Tony as comfortable as possible. "It probably didn't take," Tony said, head against Steve's chest. The younger man huffed a laugh.
"Well then, darlin', we'll just have to keep trying, won't we?"