Castiel had known his body was different to Sam and Dean’s. It was younger, smaller than the two men he followed, but that hadn’t been an issue. Castiel had, on occasion, enjoyed the fact that his body made him look defenceless. It had given him the element of surprise. It was also a hindrance in more ways than one. There were places he was not allowed to follow Sam and Dean, areas reserved for adults only and people still stopped to ask him if he shouldn’t be in school instead of trailing around behind Dean, wearing his cast offs and an oversized trenchcoat Castiel had found in a department store sale and kept for his own. It had been the first thing he had chosen.
Dean had let him keep it even though it was several sizes too large for him and a strange thing for a supposed teenage boy to want to wear. Dean had even been pleased with him, he’d said Castiel was beginning to understand free will and even getting himself a sense of nerdy style.
The other thing about his body that made it different was that Castiel was an omega. Dean and Sam were both alphas. It explained why once a month they couldn’t stand to be in the same room together without a battle for dominance. Castiel had had no choice over his body. If he had then he would have chosen to be a beta and not had to be worried by either inconvenient knots or heats.
At first he’d assumed he would be able to control his new body. He was, apparently, fifteen and Castiel had expressed some surprise at the notion that a body that young would go through heat which had given Dean something to laugh about for a good twenty minutes. Fifteen if Dean’s stories were anything to go by was plenty old enough for a heat. Still, Castiel had been completely sure he would be able to subdue such base biological functions.
As it turned out he was wrong.
The first time it happened they were in a sleazy bar that Dean knew. The owner didn’t even raise an eyebrow at Castiel’s obviously fake ID and he passed him a beer just the same as Dean’s. Castiel had drunk a little and begun to feel hot, his collar too tight and his pants uncomfortable. At first he’d thought it was the effect of drink on his young body, but when he stood up he could feel the wetness of where he’d leaked through the jeans Dean had lent him. Dean’s nostrils had flared, taking in Castiel’s scent but he wasn’t the only one. The bar had sunk into an uneasy silence, other men watching him, sniffing the air, some of them half-way out of their chairs and ready to circle him.
For a moment Castiel forgot that he was an angel, that he could burn the eyes out of every man in the bar if he wanted to and he felt scared. His body was betraying him. His hole was wet and leaking, scent rolling off him telling anyone who could smell it that he was ready to be mated. Worse was that Castiel really felt that desire. It bubbled up inside him, an aching emptiness that he knew wouldn’t be filled until he had some alpha cock in him. It was so shameful and Castiel fought to maintain his composure because he wasn’t going to lose himself and end up mated over some sticky table by a barfly he’d never see again.
Dean apparently had the same concern because a second later he had hauled Castiel up into his arms and sunk his teeth into Castiel’s neck, growling through the bite. It wasn’t knotting but it was a claim. The atmosphere in the room had relaxed and they’d been able to escape back to the car. Dean had driven them to the motel without looking at Castiel who had settled into the back seat and discovered all the ways his body enjoyed to be touched. By the time they had reached the safety of the motel and Sam, Castiel had three fingers in his ass and had come messily over his front. That had taken the edge off and Sam didn’t ask about the dark purple bruise at Castiel’s throat that refused to go away no matter how many times Castiel tried to heal it.
Only time caused it to fade.
Dean watched him constantly throughout the next month, obviously wondering when the heat would strike again but Castiel had been almost convinced that now he knew what a heat felt like he’d be able to prevent it from happening a second time round.
The second time it hit, when Dean had to stab a demon, was something Castiel preferred not to think about.
The third and fourth times were also near misses. Castiel’s heats became more frequent, stronger. He found himself going willingly with men he would never have spared a second glance if it wasn’t for his heat and it was only Dean’s vigilance that prevented him from ending up mated to some creature from Hell.
Finally Castiel had to submit to the idea that his heats weren’t something he could control. Instead they were something which controlled him. He was no longer a weapon for Sam and Dean but a liability. Dean never left his side unless strictly necessary during the heats. He watched Castiel, watched every man watching him and was ready with a possessive gesture whenever things became too much.
If Castiel had been better versed in the study of human nature, and the nature of alphas when they had chosen a mate, then he might have seen what was coming but as it was he was blissfully unaware until it happened.
Castiel was still unsure how he’d ended up over the hood of the Impala, his pants around his ankles with Dean’s cock thrusting relentlessly into him. One moment they had been driving along, Castiel with his legs spread wide, fingering himself in a distracted way. His fingers had long ago ceased to be enough but Castiel still touched himself out of habit. It felt good and it did something to abate the ache inside him. Castiel was hardly paying attention to the outside world. They were driving through some wooded area but he didn’t really care. Then Dean made a sudden turn, pulling them off the main road and up a little side road to a picnic area. It was growing dark, they were the only car when they parked up. For a second Castiel thought Dean was going to get out and take a leak but instead Dean’s breathing became harsher and he gripped the steering wheel tightly in both hands, his nails digging into the leather.
When he turned his head his eyes were dark with lust.
“Castiel, tell me you want this or get out the car and get somewhere safe because I can’t anymore,” Dean’s voice broke on the last word, strained and desperate and for the first time Castiel could scent the arousal rolling off Dean in waves. His eyes drifted down the bulge straining in Dean’s pants and he squirmed in his seat. Dean’s knot would fill him up nicely.
Castiel considered Dean for a moment, wondering if he shouldn’t run away. Dean was a human, he was stubborn and difficult but he was also kind, caring. He had a great capacity for love. Even with the pressure of Castiel’s heat, having Castiel with him so close and so ready, he had controlled himself and was still controlling himself, offering Castiel a choice.
Castiel couldn’t think of anyone else he would rather be mated to.
His consent, he conceded, had been how he ended up over the hood, Dean’s swollen cock pulsing inside of him, driving him to distraction. Everything about Dean was so much bigger than he’d realized it would be. Dean’s cock was huge, stretching him wide and his body covered Castiel’s as he bent over him, driving in deep. Castiel scrabbled for some kind of grip but his fingers slid across the polished hood of the Impala and his toes scrapped across the ground as Dean impaled himself deep in him again. With every thrust Castiel could feel the base of Dean’s cock swelling, the knot growing there. Soon Dean would come and he’d lock all of that away inside Castiel, deep in and keep it that way until he was sated.
“Fuck, look at you, taking everything,” Dean murmured in his ear, words hot and breathless, “Thought about this so much, Cas. Wanted you in that bar, wanted to bend you over the table and fuck you in front of all those guys, knot you so they knew you were mine. You look so pretty taking my knot, Cas. I’m gonna breed you up good, make sure you never look at another man again.”
Suddenly his grip shifted, hands on Castiel’s hips dragging him up and Castiel clutch helplessly at the air because he was being lifted up, supported only by Dean’s hands on him and Dean’s rock hard cock. Castiel had thought he’d taken every inch of him but now he knew that wasn’t true. Now he really was impaled on Dean’s cock, everything buried in him right up to the knot and there was no remorse from it.
“You’re so light, Cas, so small. I always wondered if I could fuck you like this, hold you up by my cock. Look how hard you got me, baby.”
“Dean, Dean,” Castiel sobbed, wiggling but Dean’s grip on him tightened, his thrust slowing, knot catching at Castiel’s rim and then he was still. A second later Castiel was flooded with warmth, Dean’s cock pumping into him every last bit. Castiel finally felt full. His own cock jerked and he came as well, splashing on the floor underneath them. He clenched tight, certain he didn’t want to lose a drop of Dean’s come from inside him but Dean’s knot was seeing to that. Dean groaned, nuzzling at his neck, nipping and biting.
“You’re so hot, Cas. My good boy, do you like that?” he asked, his voice low and rough, his cock still painfully hard inside Castiel. It felt so good, everything he had been missing and desperately wanted.
“Yes,” Castiel groaned in response. He didn’t care how long he stayed like that, stayed trapped on Dean’s cock as long as Dean kept filling him, kept shooting into him, had him mated properly. Castiel knew after this he would never leave Dean’s side again. Why would he go looking for anyone else when he had an alpha with a perfect knot right here?
And more than just a perfect knot because that alpha was Dean, and Dean had let him choose.