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Whenever John was away on a hunt Sam and Dean had as many of their secret make out sessions as they had time for, enjoying each other’s mouths for long, breathless stretches of time on hard motel room beds. The rules Dean had set were that all clothes had to be kept on, and no touching of cocks or asses was allowed, even through clothes. Sam often tried to negotiate - “just a hand job, Dean,” he’d beg with those puppy dog eyes, and it would make Dean ache to deny him. Dean had to remind himself over and again that he couldn’t let it go too far; Sam was only twelve, and they were brothers, and it was probably wrong to be doing anything sexual at all, but Dean was only sixteen and he was good at putting lust first and logic second. He justified what they did because he had drawn a clear line; it was only kissing. No hand jobs, no blow jobs, no anal sex, just kissing. What could kissing hurt? Family members kissed sometimes… fine, so what he and Sam shared wasn’t the same kind of kiss you’d normally share with a family member, but did the intensity level of the kiss really matter? Wasn’t it a blurry line? Dean’s libido had convinced his mind that the line was blurry enough to excuse their long, passionate lip-locks.
One night the brothers lay beside one another on a motel room bed, fully dressed and kissing each other madly. Sam was on his back with a pillow beneath his head and Dean was hovering partially over him, but he kept his bottom half held carefully away. Dean relished the sensation of Sam’s tongue undulating against his own, of his lips pressing, of the warmth and scent of his nearness. He caressed Sam’s tongue with his own tongue, and he ran his fingers through Sam’s soft hair. He held Sam’s face in his hands and kissed him wildly, needily. As their mouths lavished attention on one another Dean strained to ignore his screaming erection - he had to ignore it. He wondered if Sam was hard too, but he repressed the urge to glance at Sam’s crotch and see if there was a bulge in his pants.
When Dean moved his mouth to Sam’s neck and pressed his lips to the skin, Sam panted for a moment, then spoke.
“Dean,” Sam said, “listen, I know you don’t want us to have any kind of sex, but -”
“Sammy,” Dean interrupted, pulling his head away, “I have to draw a line. We can excuse what we do, I mean, it’s only kissing, right? But we can’t fuck or even touch each other’s cocks or asses, so, you know, no hand jobs or blow jobs and for sure I’m not fucking your ass so don’t bother asking again.” Dean desperately hoped Sam would listen about not asking to be fucked; it was especially painful for Dean each time he had to say no to that particular invitation. “And,” Dean remembered to add, “clothes always stay on. Those are the rules, and you know it.”
“Well, if you would just compromise a little,” Sam said, a lustful, beckoning glint in his eye and a soft, sweet tone in his voice, “on the nudity part, I read about something in the library today.”
Dean thought for a moment - nudity wasn’t really that bad, was it? Brothers sometimes saw each other naked anyway, changing in front of each other. That was normal. This wasn’t so different…
“Tell me,” Dean replied, already wanting to give in to whatever it was, straining to keep his mind steady, to force it to think clearly in the face of his arousal.
“It’s a practice that was common in ancient Greece,” Sam explained, his sweet tone growing sultry, “called intercrural sex, where one person fucks the space between the other person’s pressed together thighs.”
Dean’s mouth went dry at the thought of it. His hard cock pulsed.
“That’s not only breaking the nudity rule, it’s breaking the cock touching rule too,” Dean pointed out, too big a part of him hoping that Sam had an excuse they could cling to, a justification for the thigh fucking.
“I guess,” Sam replied, “but your cock would only be touching my thighs, not my cock or ass, and not my mouth or hand either, so isn’t it kind of a compromise? It’s not sex at all, not really. You said no hand jobs or blow jobs or anal sex, but this is its own thing. It’s a loophole, you know? Come on, Dean, no one would ever think of rubbing between someone’s thighs if you asked them what counted as sex, right?”
“Sammy,” Dean made himself say, hearing his voice come out as a harsh whisper as he struggled to resist, strained to forbid the action despite his longing to accept the excuse Sam had provided, “we shouldn’t.”
Sam leaned in and breathed warm against Dean’s ear. Dean shivered with arousal.
“Are you sure?” Sam whispered.
Dean felt a hot thrill throughout his body and a heavy throb throughout his cock and he lost control, giving in and grasping onto the justification Sam had created. Hungrily, urgently, Dean stripped Sam’s shirt and then his own.
“Oh, Dean,” Sam spoke with relief, with profound lust and with rich affection.
Dean hurried to shed his pants and boxers and then removed Sam’s. He gazed at Sam’s bare body with wide eyes. He wanted to kiss Sam’s skin all over, but that seemed like something he should stop himself from doing.
“Dean,” Sam moaned softly, and Dean leaned in and kissed Sam’s skin anyway, covering Sam’s shoulders and chest and stomach with fond presses of his lips as Sam made small, breathy sounds. When Dean reached Sam’s hard cock, he stopped himself from bringing his mouth to it, or even wrapping his hand around it; Dean didn’t know how to justify a hand job or a blow job. Sure, a hand job or blow job would be better than fucking Sam’s ass, but manual and oral sex were still well-established forms of sexual activity. Rubbing between Sam’s thighs, on the other hand, wasn’t really any kind of sex. It wasn’t really anything at all, or at least it was obscure enough that Dean could convince himself that it wasn’t really anything at all. It was a loophole, like Sam said. A totally valid loophole.
Dean sat up, pulling himself reluctantly away from Sam’s body because he was afraid his mouth would land on Sam’s cock before he could stop it. Sam got up and bent over the edge of the bed. He held his legs flush together.
“Come on,” Sam moaned, “fuck my thighs. It’s not real sex, it’s okay. Don’t worry, Dean.”
With his hard cock in his hand, Dean stepped behind Sam’s bent over body. He paused; should he stop? Dean knew he should not have sex with his underage brother, but like Sam said, this wasn’t really sex…
Dean took a deep breath and brought the head of his cock to the crevice created by Sam’s pressed together thighs.
“Do it,” Sam groaned, “I want to make you come, I want it so badly, Dean, please do it, it’s okay, it’s not sex.”
Dean made a wild noise and slid into the space. It was warm and the skin of Sam’s thighs was silky. Dean allowed himself to hold onto Sam’s hips and he began to thrust his cock in and out of the area, the friction making him moan and swear. Sam made a blissful sound and began to grind his cock against the bed beneath him.
“Let’s pretend you’re fucking my ass,” Sam spoke wantonly.
“Okay, Sammy,” Dean replied huskily, overwhelmed by his lust. He gazed down at Sam’s ass as he fucked Sam’s thighs. Sam’s ass was perfect, and Dean longed to touch it, to caress it and squeeze it, to touch its hole and…
No, all of that was wrong. Just the thighs, that was the loophole, that was the compromise, that was the new line.
“You feel so fucking good inside my ass,” Sam roleplayed, “fuck me, fuck my ass, Dean.”
“Oh, fuck, Sammy,” Dean groaned, feeling almost like he was actually inside Sam’s ass but also feeling profoundly frustrated that he wasn’t. “Sammy, your ass feels so good around my cock, oh, I’ve wanted this.”
“Me too,” Sam moaned, humping the bed madly as Dean thrust his hips, rubbing his cock again and again between Sam’s thighs, staring at Sam’s ass, staring, staring… it was okay as long as he didn’t touch it. “Dean,” Sam spoke with fervor, “when we kiss I think about you fucking me, about how you’d feel inside me.”
“Does it feel like you imagined?” Dean moaned, enjoying the game, snapping his hips faster, rushing between Sam’s thighs over and over.
“Better, better than I ever could have imagined,” Sam replied desperately. His tone was full of frustrated longing, and Dean felt it too; the game was fun, but it didn’t satisfy his yearning for the real thing. Still, it was amazing, and it would have to be enough. Dean couldn’t let it go any further, he reminded himself, he could never let it go any further… well, unless they found another loophole or…
“Won’t you please touch my ass,” Sam begged, sounding like he had fallen out of the game, sounding raw.
“I don’t think I should,” Dean replied, but then he did, grabbing it with both hands and massaging the cheeks even though he had no excuse.
“That feels so good,” Sam breathed, “I wish you would fuck my ass for real, oh Dean, will you?”
“Sammy,” Dean groaned, wanting to say - yes, yes, let me suck you and lick you and fuck you and then do it all over and over again until we’ve both come and come and come, until we can’t come any more, until we’re so exhausted that we fall asleep naked and sweaty in each other’s arms... But then Dean reminded himself that, incest aside, Sam was only twelve and that was too young to be fucked, no matter how much Sam wanted it.
“Please,” Sam spoke smoothly, “no one will know, it will feel so good.”
“When you’re older,” Dean heard himself reply, knowing that was probably wrong too because no matter how old Sam got they would still be brothers, but also knowing that he meant it, that when Sam was old enough Dean would find a justification for them to fuck for real. He would find an excuse, somehow. He had years to think of something.
“Okay, Dean,” Sam replied softly, his tone a mix of disappointment and excitement, “I’m holding you to that.”
Dean moaned loudly as Sam squeezed his thighs more fiercely together, pressing Dean’s erection tightly between them, surrounding Dean’s eager cock with his flesh as Dean drew it briskly in and out of the slim space. Dean caressed Sam’s ass cheeks, squeezed them and massaged them, but successfully fought the urge to slip a finger between them.
“You wanna come together, Sammy?” Dean groaned, thrusting rapidly.
“If you promise we can do this again,” Sam panted as he worked his own hips frantically, rutting against the bed beneath him.
“Promise,” Dean let himself say, and he meant it - this was the new line, just making out and thigh fucking, and that would be the line until they found a way to push it even further. “Ready to come?” Dean asked with heavy breath.
“Tell me when, Dean.”
Dean gave a final, brutal thrust and called -
“Now, Sammy.”
Dean swore and spilled his seed between Sam’s thighs as he watched Sam convulse and listened with ecstasy to Sam’s long, wild cry. As Dean came down from his climax, he dreamily stroked a hand down Sam’s back and smiled. Dean had feared he would feel a rush of shame and guilt in the moment following his release, but when he thought about their taboo, forbidden act, Dean felt only a keen thrill, and when he thought about their nearness, about the pleasure they had shared between them, he felt only boundless love for his little brother, for the person who was most dear to him in all the world.