It’s been a long time since he’s been with anyone. Since Claudia died, John felt no urge to look for someone else, someone new. But that doesn’t mean that his sex drive went away.
He usually keeps it in check by jerking off whenever he can, but it’s been a long few years and Stiles is just getting to the age where John can’t explain his moans by shrugging them off as aches and pains. He can’t really hide the scent of his come either, not now that Stiles is starting to recognize it, his own puberty slowly creeping in.
They had the discussion about what happens, about waking up with morning wood and sometimes sticky sheets. John just didn’t expect that to happen to him. He thought it would be Stiles’s sheets that would need frequent changing. And they do, but they’re not the only ones. In sync with Stiles’s growing, John feels like he’s reverted back to his teen years, frequently waking up hard and leaking, cock standing to attention and sometimes — he doesn’t really remember the dreams he’s having but they must be interesting — to come all over his crotch, his cock softening as he wakes.
Later, he starts remembering fractions of the dreams. He remembers soft skin under his hands, the feeling of his cock surrounded by wet heat and the tightness that it thrusts into. He wakes up a time or two with his hand already wrapped around his length and stroking, fading images of an ass it’s being thrust into lingering on the edges of his mind. It's not a surprise, while he's never come out, he has experiences with anal sex, not just with Claudia but from college too. He remembers how good it felt to have his dick surrounded by that tightness.
It feels like another dream when he wakes up that morning. His hips thrust up and at first, he thinks that he's still not fully conscious, his mind perking up at the possibility of remembering more details this time. Then, as he slowly starts emerging from the fog of sleep, he realizes that his arms are up, hands slipped underneath his head.
And yet his cock, even as John regains consciousness though he keeps his eyes closed, still feels like it's inside something wet and slick, something that moves up and down the length, a weight settling on his hips on every downstroke. He can't help the instinctual reaction to thrust his hips up but he freezes when a quiet moan fills the room, one that is not his own.
John slowly slips his hands from under his head and drops his arms down to where his own hips should be. Instead, his palms are met with soft skin and narrow hips that keep rising and falling. Not looking yet, though his heart stutters as his mind begins to put things together, John moves his palms along the skin, his hands big on the thin limbs that he's stroking over, feeling them tremble underneath his touch. He moves the hands back up over the crease of narrow hips and to slender sides.
He knows. He knows but he can't open his eyes and look, to have proof of what his mind has already figured out. Instead, he grips the sides tighter and lets the body move a few times before he guides it, pushing it down as he thrusts his hips up.
"Daaaaad," a moan echoes around the room.
There's no more denying, no more pretending that this is just a dream as small hands land on his stomach and brace on it while the rest of the slim body continues rocking, the hole tight and wet around his cock.
John opens his eyes with terror rushing through him as he sees his son's body on top of him, a sheen of sweat covering his face and chest, eyes wide and lips parted as he lets out a gasp with every move down.
At that moment, John grips Stiles's hips tight and stops him from moving. It's wrong. It shouldn't be happening. He can't.
And yet, as he keeps staring at Stiles biting his bottom lip, a panicked look rising in his flushed face, John's brain does something he didn't expect. It floods him with images of this, of other times that he knows must be from the dreams he's been having. It shows him that he's been thinking about this subconsciously for a long time.
Then Stiles shivers and his hole clenches around John's cock. It feels good. It's enough that John's hips thrust up automatically and the hands that are on Stiles's sides jerk down, pushing the boy onto John's throbbing cock. Stiles's eyes light up in response and he starts moving again, licking his lips as he rocks his hips up and down, John's cock sliding in and out of his tight hole.
Stiles's cock is leaking onto John's stomach and when John looks down he sees how red it is, how hard, the head covered with come drops, the cock small between their bodies.
They don't talk. John is afraid of what might come out of his mouth if he speaks. Not talking makes it possible to think that this is a dream, that he's not really fucking up into his son's ass and that his balls aren't tightening at the thought of filling Stiles up with come.
Now that they're both awake though and with John helping Stiles move in a steadier rhythm, it doesn't take long before they both topple over the edge of an orgasm. Stiles is first, sitting up and arching his back with a hard thrust down onto John's cock, his own smaller one spurting come across John's chest, his lips open as he moans and trembles. His hole clamps down on John's dick and that sends John hurtling into his own orgasm. His hips jerk up and he holds Stiles down as his cock throbs inside the tight hole, come filling it as he shakes with the strength of the climax.
Neither of them moves until Stiles slumps forward and braces himself on John's chest again, breathing heavily as he looks down, his face still flushed and his eyes sparkling with the oh very familiar mischief.
John gently lifts him off his softening cock and Stiles whimpers at the loss but doesn't fight it. He slides on the bed by John's side and immediately curls his naked body against John's, then looks up with an expression that John figures is supposed to be remorse, but Stiles's eyes are too bright to sell it.
"Are you mad, Daddy?" Stiles asks between labored breaths.
"I don't know," John admits.
He should be. This is a line that shouldn't have been crossed, it's something that he knows should never happen between a father and a son, even more so because Stiles is decidedly under the age of majority.
"I was hoping you wouldn't be," Stiles says quietly, now sounding a little more guilty. "I wanted to... I came here before, you know?"
"I don't," John says, eyes widening in startling realization. "When?"
"In the night. When I was afraid and wanted to sleep here. And you had dreams."
"And I was curious."
Shocking, John's inner voice snarks.
He loses all the snark when Stiles tells him in rapid-fire rambling about how he first touched with his hands when he saw John's cock hard. How he'd come in on purpose when he heard John moaning in his sleep, how he put his lips around Daddy's cock and how nice it was.
One of the lingering thoughts on his mind is that he can't do this because Stiles doesn't know what he wants. But as John listens to Stiles talk more about how he'd be in here while John was sleeping, how he'd suck John's cock while he was fingering his tight virgin hole at the same time, all that goes away.
"You want this," John says when Stiles pauses for a breath.
"Mhm. You're not mad, Daddy, are you?"
John knows that he can't get hard again just yet, but his cock still makes a valiant effort when he sees Stiles's wide eyes filled with innocence and when he feels the small cock harden again against his side. Whatever battle he was fighting in his mind that would have stopped him is lost when Stiles bites down on his trembling bottom lip.
"Not mad. But I think it's time I got to have some fun," John tells him and tilts his chin up so he can lean in for a kiss.
He's going to hell. He might as well keep going.