Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/12013824.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      M/M
  Fandom:
      Supernatural
  Relationship:
      Castiel/Dean_Winchester/Sam_Winchester, Castiel/Dean_Winchester, Dean
      Winchester/Sam_Winchester, Castiel/Sam_Winchester
  Character:
      Dean_Winchester, Castiel_(Supernatural), Sam_Winchester
  Additional Tags:
      Alpha/Beta/Omega_Dynamics, Alpha_Dean, Alpha_Sam, Omega_Castiel,
      Knotting, Double_Penetration, Consensual_Underage_Sex, Incest, Sibling
      Incest, Breeding, Come_Eating, Come_Swallowing, Come_Marking, Come
      Inflation, Marking, Claiming, Claiming_Bites, Threesome_-_M/M/M,
      Polyamory, Polyamory_Negotiations
  Stats:
      Published: 2017-09-06 Words: 1324
****** He's in My System ******
by ADevilsHunger_(Dream_tempo)
Summary
     Sam's a virgin and his incessant masturbating is driving Dean up a
     wall. He figures getting his brother laid will solve the problem, and
     who better to solve that problem than the omega he knows best, his
     boyfriend Castiel? Ingenious idea really, he'll even show Sam how to
     do it right. Now he's just gotta sell it to Cas.
Notes
     A follower prompt that I felt was a little too long to put in my
     collected drabbles. Hope you guys like.
“C’mon baby, us alpha’s gotta pass it on. You really want him out there, first
date, never having popped a knot? He’ll scare himself!” Dean was plastered to
his boyfriend’s side, whining and pouting as best as he could, even turning it
to eleven playing with Cas’ hair and lipping at his ear and trailing a hand up
under his shirt and over his hairy belly. 
Cas just gave him a look. That look. The one that said he’d never bought a
single ounce of bullshit from a Winchester, ever in his life. Especially not
Dean. “Sam’s fifteen. He’s probably knotted his own fist more times than I can
count.” 
Dean couldn’t help his grin breaking out, eyebrows waggling as he chuckled at
his boyfriend’s unamused side-eye. “You don’t even know, babe. He whacks it
like it’ll fall off if he doesn’t keep it up. I swear to god his hands just
smell like spunk now, that’s just the way they are.” 
“And that’s the real reason, right? You know he’s all blue balled and you wanna
give him to the hook-up? Make sure his first omega is one that’ll make his dick
ache?” Dean looked perfectly pleased, smile practically feline as Cas just
shook his head, doing his best not to break out into a smile. 
“C’mon! The kid works so hard and gets straight A’s and I know you get his nuts
all a-throbbing. Every time we make out on the couch I can smell his boner a
mile away. I’ve even caught him rubbing it in the dirt sheets after, sniffing
and sucking at our wet spot-- you shoulda seen him blow! Kid’s a real super
soaker.” 
Dean looks nothing but pleased, the gleaming eyes of a proud papa, swear to god
close to squeezing out a tear. “I’ll go first,” he assures, gripping Cas’
shoulder and suddenly switching to deadly serious. “I’ll prep you and show him
how to get a rhythm, show him how to ease the knot in, make sure he hits your
button and doesn’t try to pull out too early even if I have to hold his hips
and make the motion of the ocean myself, alright? 
You’ll be all loose from me anyway and he’s got a fuckin’ thigh slapper, but
it’s still slender babe, like a finger. You’ll be so wet by then, boycock won’t
even feel like anything. And I’ll even eat you out after! I know you like it
when I get sloppy, baby, and I’m not joking, he’ll cream your ass like he’s
churning butter and we can share all of it. I’ll even--” 
“Dean!” Cas has one hand over his face, but his shoulders are shaking as he
uses the other to press it to his boyfriend’s lips, anything to get him to slow
it on down. “Not that you’re not making me soak straight through my pants, but
I was already gonna say yes.” 
“Really?”
Cas snorts, shaking his head fondly as he leans over to kiss Dean, soft and
slow and sweet. “Ya. Sam’s always nice to me and I can tell it really means a
lot to you and you know I’ve always wanted to be dp’ed. Just tell Benny we
already found someone and I’ll come over Friday.” Dean’s face is totally blank,
brain fried as spunk starts filtering through his jeans. 
===============================================================================
 
“This is not at all what I dreamed about when I first got off to this,” Dean
mutters, eyes wide, awe in his voice as he holds his boyfriend while the small
boy slowly starts lowering himself into a crouch. His hands are on Cas’ hips,
Cas’ hands are on his and Sammy’s thighs, Sammy’s hands are holding the
brother’s dicks together, heads pressed tight and leaking as Cas’ hole starts
to sink down over them. 
He moans, head jerking as he can’t decide whether to stare at Cas’ face, his
cock, or Sammy’s oblong balls as they jerk in pleasure. The two Winchesters are
almost sitting in each other’s laps, thighs overlapping, balls pooling
together, dicks rubbing as Castiel rocks gently between them. 
“You’ve been having wet dreams about me?” Sammy squeaks, adorable, little face
bright red as Dean starts moving, gliding his shorter, but much thicker dick
along his baby brother’s long, slender one. 
“How am I not supposed to? You sleep five feet away and jerk off like three
times a day. And you’re not exactly quiet about it.” Cas rolls his eyes, even
as he’s clenching around them and his thighs start quaking while he lowers and
raises himself. 
Sammy’s face gets even redder and he buries it in the back of Cas’ shoulders,
bear hugging the older boy from behind and whimpering as his hips judder, the
base of his cock already swelling and firming up, signaling his need to
breed. “Stop bickering you two and just fuck me! I swear I’ll choke you both
out if you come before I do.” 
“Kinky,” Dean snickers before taking his boyfriend’s mouth in a wet, smacking
kiss, both of them moaning and being sloppy with it, tongues lapping at lips,
teeth scraping chins. Sam just whines at the show, jets enough pre that it’s
sliding down his shaft and into his pubes, holding on for dear life. 
Cas pulls away to jerk his head toward the boy, gives Dean another look and
then stops moving. “Hey kiddo, it’s alright, just relax. Look at me, I got you.
I’ve always got you.” They connect eyes over Cas’ shoulder, lean forward, start
to suck and kiss and moan just as heated as Cas and Sam did. 
Their hips start to piston, moving in counter intervals, giving slick, hot
friction both to Cas’ inside and both of their throbbing shafts. Their hairy
low hangers start to slap together, wet skin sounds ringing out through the
room. They don’t break away, the brothers leaning further and further into each
other, smothering Cas between them. Their breaths are deep and desperate
through their noses, mouths wide as they can get them, needy, hurt sounds
floating out between. 
And no one know how, when, who went first, but suddenly they’re stuck. Cas’
stomach is bloating like he’s already several months knocked up and they’re all
sweating and moaning as frothing jizz gushes between them. Cas’ thighs are
shaking, Dean’s feet are curling up, Sam’s balls are drawing tighter and
tighter, throbbing with each pulse of his heady cum. 
Dean grabs him by his little ass to pull him in tighter, usher his knot deeper,
continue to rub their gushing dicks together. They grind as Cas writhes and
they start sucking bruises all over his skin. 
It’s over a half hour before they slip loose, soft enough to pop out with a
sticky sound and all three fall to the sheets, chests heaving. Cas is leaking
it all out his ass like a faucet, but just like Dean promised, he immediately
dives down, putting those pretty lips to use sealing over his wrecked hole as
he makes sloppy, sated noises scooping it all out with his tongue and holding
it in his cheeks. 
After some hesitation, Sammy joins him in this too, their tongues tangling and
the mess dribbling down their chins as they try to vie for space. Cas mewls as
he runs his hands through their hair, pats their cheeks, spreads his legs for
them again. 
The boys come back eventually, both looking like eager puppies as they bear
down on him with mouths sticky and salty and reeking of musk. There’s just no
coordination, but they chuckle as they try and share the mess, bumping noses
and temples, Dean getting possessive and wrapping Cas up in his arms, Sammy
happily curling up behind his big brother, tangling their legs and burying his
cute nose in Dean’s sweaty nape. 
The kid never does go on that date, after all, his brother already found
the perfect omega. 
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