Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/4927255.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      M/M
  Fandom:
      Supernatural
  Relationship:
      Dean_Winchester/Sam_Winchester
  Additional Tags:
      Mpreg, Alpha/Beta/Omega_Dynamics, Lactation_Kink, Teen_Pregnancy, Sibling
      Incest, Feminization, Large_Breasts
  Stats:
      Published: 2015-10-04 Words: 3642
****** Ripe Omegas Are The Best ******
by nerdygaycas
Summary
     Sam presents as an Omega when he's 12. He's so beautiful, all curvy
     and soft, that by the time he's 14 Dean can't keep his hands off of
     him. Dean wants to breed Sam but first he'll make the Omega take some
     very special pills to make sure he gets really knocked up.
Notes
     Full prompt:
     Sam never goes through an awkward phase. From the moment he presents
     as Omega at 12 he's beautiful and by the time he's 14 he's pretty
     perfect. Dean can't get enough of his brother and they've been
     messing around for a while. Sam is the right kind of soft and curvy
     and the type of Omega that develops breasts (sizable ones at that)
     before ever becoming pregnant. Dean eventually can't get the idea of
     breeding Sam out of his head. For whatever reason he doesn't present
     the idea to Sam. Dean actually suggests that Sam goes on birth
     control saying that it will make him even bustier and then Dean can
     properly knot him. Sam is completely on bored and starts taking the
     pills. He puts on weight (maybe even getting a little bit of a
     belly), his breasts increase in size (shirts straining) and he gets
     hornier. Eventually Dean starts knotting him.
     Only Dean never gave Sam birth control. The pills increase hormones
     and fertility. Sam is pregnant. Very pregnant. Very very pregnant. (3
     - 7 babies)
     Dean worships Sam's changing body which gets bigger and fuller with
     each day.
     How Sam reacts is up to author maybe he's furious and stays mad or he
     comes around or he's really excited and loves the feeling. Just as
     long as he does stay pregnant and with Dean.
See the end of the work for more notes
Dean remembered making fun of Omegas back when he was thirteen. At the young
age of eleven Dean had presented undoubtedly as an Alpha, and Alphas for the
most part stayed the same, showing a few signs here and there of their rank but
nothing more.
Omegas’ puberty, though, that was a different affair. Omegas got their hormone
levels all over the place resulting in embarrassing breakouts, hips widening to
evidence their new acquired fertility, pheromones intoxicating the atmosphere,
unaccountable mood swing and occasionally the growth of breasts, though it was
a very uncommon occurrence. Breasts only developed if the omega was pregnant,
but every once in a while there’d be a confused young omega with enlarged
nipples showing through their shirt.
Back then Dean could not take new Omegas seriously. They were as puzzled by the
changes taking place in their bodies, they were going through what he called
“awkward phase”, and so in reality he only did pay attention to older Omegas.
Three years have passed though, and Dean’s a bit more mature if anything.
Taking care of a little brother 24/7 will do that to you. Dean’s been fully
responsible of Sam since their father left never to come back.
Dean got them a little apartment. His check isn’t much so the only place he
could rent was a small studio; it’s no ‘apartment’ by any definition. There are
no rooms, only a small kitchen and a bathroom, so Dean and Sammy end up sharing
well… everything.
Being an Alpha born from an Alpha father and a Beta mother, Dean never though
Sammy would present as anything else than that, but to his utter surprise, Sam
presented as an Omega when he was barely 12 years old.
Dean had come home from his late night shift, took a shower and after putting
on his boxers, went straight to bed. He wrapped his arms around the young body
that lied on the mattress next to him.
Immediately Dean noticed Sammy’s body was very, very warm. Fear gripped him
thinking Sam was sick, they’d have to get him medicine and lower his fever
somehow. Shit, maybe they’d even have to go to the hospital.
“Sammy, hey, wake up, angel” said Dean whispering, trying to coax Sam from his
sleep.
Dean took off the covers. It was usual for Sam to sleep stark naked so that
didn’t surprise Dean, what did made him wide eyed was the hardness of his
brother’s dick. Sam wasn’t one to pop boners in his sleep, he was too young for
that, Dean thought.
More surprising than an erect cock was the sweat pearls covering his body, but
even more so the dampness of the sheets around his ass.
Dean hurried to turn the lights on and yeah, definitely a case of wet sheets.
Then along came the strong smell of heat permeating Dean’s nostrils, he felt
his cock hardening at the beautiful sight that Sam was, sprawled naked on their
bed, juices slipping out of him, dick twitching.
He seemed to be muttering something in his sleep. Dean stepped closer and sat
next to him on the bed.
“Dean…” the name was spoken so softly, but Dean could hear the pain and
desperation with which it was uttered.
“I’m here, Sammy. Brother will take good care of you.”
Dean kissed Sam’s forehead and teased the rim of his ass, marveling at the
slick coming out in spurts. He pushed his finger inside all the way, digit
surrounded by the delicious warmth of his baby brother’s asshole.
Soon there were two fingers pumping Sam’s hole, the young boy was rolling his
hips, feet firmly planted on the bed. Dean was massaging his own cock through
the fabric of his boxers and then, the very exact moment Dean pushed against
Sammy’s prostate, that little bundle of nerves, the Omega’s eyes jerked wide
open.
“Dean?” he asked, worry all over his face.
Dean caressed his hair as he kept thrusting his fingers mercilessly into the
tight hole, Sammy was still rolling his hips trying to get the fingers to fuck
him deeper.
“Shhh, it’s okay. I’m here, Sammy. It’s just your heat, okay? I’m just helping
you.”
Sam’s back arched as he moaned loudly, Dean caressed the bud deep inside him
and then Sam was coming all over his belly, white stripes adorning his taut
belly.
“I’m… an Omega” the words came softly, as if Sam had uttered them to himself,
forgetting about Dean’s presence.
“Yes, you are, Sammy” said Dean, fingers coming out.
Sam felt empty instantly, he could feel his ass trying to clench around
something. The sensation was a bit disconcerting but not entirely unpleasant.
Dean signaled him to open his mouth and Sam always did what Dean said, so he
did. He could taste his own slick on Dean’s fingers, the taste was sweeter than
he had imagined, and thick in its consistency.
“Your slick’s very sweet, Sammy, the sweetest I’ve ever tasted… You’ll be such
a beautiful omega, little brother” a smile on Dean’s lips.
Sam kept suckling Dean’s fingers till he fell asleep. Cuddling as close as they
were Dean felt the poking of Sam’s dick all night, his thigh wet from the slick
dripping from Sam’s hole. His own cock was rock hard, he was afraid to pop a
knot but first came his duty to Sam, so this was his place and here he would
stay.
Sam skipped school the whole week. Dean bought him some toys to help him go
through the heat. Two dildos, the smaller barely six inches and the bigger was
eight. Dean also got him a vibrating plug.
Unfortunately Dean wasn’t home most of the time, he had to start working double
shifts to give his little Omega brother the best.
During Sam’s heat peak he would often fantasize about his brother coming home
and taking him from behind, fucking him with his cock and knotting him, then
there’d be no need for plastic toys, but he knew that wasn’t very likely. The
most Dean would do to him was finger him late at night, he even kissed his hole
once, but he didn’t do it again so Sam was pretty sure Dean didn’t like him in
that way.
By the sixth and last day of his heat, Sam was exhausted. His limbs ached and
the hunger of his insides was finally subsiding.
It was a Sunday so Dean didn’t have to work. He woke up at almost 10am to the
smell of eggs and bacon, and then he saw Sam.
Pretty young Omega was naked as usual but Dean noticed something different, his
skin seemed to be… glowing somehow, that and his hips were definitely a bit
curvy. In fact, he wasn’t all sharp angles anymore, his lines were all softer,
Dean could’ve sworn.
The growling of his stomach brought him back from his musings and he hurried to
brush his teeth and have some breakfast.
 
Over the following weeks Sam’s change was more obvious, though at times Dean
thought his eyes were playing tricks on him.
The curves of Sam’s body became more pronounced. Compared to the boy he’d been
some time ago, now Sammy’s Omega was definitely showing. Dean couldn’t keep his
cock from going hard when he saw Sam doing something as simple as sweeping the
floor or cooking, or sleeping, or anything really.
Dean hated Sam going to school, all those too young alphas lusting after the
perfect Omega his little brother was becoming. He worried constantly about
strangers taking advantage of him, mating him without his consent, or… just
mating him really. He couldn’t bear the thought of it so for his own good Dean
decided to have Sam drop out of school.
Sam didn’t care much about it, he was happier anyway when he was home with
Dean.
And so the months passed, Sam’s body changing beautifully right before Dean’s
eyes.
 
Now the alpha can’t keep his hands from touching the omega’s body and Sam
doesn’t seem to mind in the slightest.
Sammy is thirteen and such a wonderful sight to the eye. His waist contrasts
with the soft edges of his fertile hips, his ass so plump and round, jiggling
shyly when he walks. He’s gained a few pounds but oh god do they suit him. It
all adds to the image of ripeness he presents and to Dean’s delight Sammy has
started growing breasts as well. He turned out to be one of those rare Omegas
and Dean couldn’t be more grateful.
The two mounds of flesh fit perfectly in Dean’s hands. He know because he can’t
keep himself from fondling them.
Dean still helps Sam through his heats, though he won’t fuck him with his cock.
Now Sam doesn’t only get Dean’s fingers to fuck him, his brother will eat his
ass and delve his tongue into the throbbing heat without even having to ask him
to do it.
Dean also lets him suck his cock and Sam’s so addicted to it. He’ll wake up in
the middle of the night to wrap his lips around the soft flesh and have it
harden inside his mouth. The Omega loves swallowing his big brother’s come, it
makes him healthier and more docile, and as an Omega it’s all he really needs.
By the time Sam hits fourteen Dean is officially a slave to his brother. He’s
the perfect representation of what an Omega should be and look like. He’s that
beautiful. They start fucking though Dean won’t knot him, which frustrates Sam
to no end.
“Not yet” Dean says, taking his cock out and pushing it inside Sam’s mouth,
it’s the best way to stop Sam from arguing.
And as Sam sucks on his brother’s length, he grabs a hold of the biggest dildo
he owns, 9 inches, and starts fucking his hole raw on it.
Sam whimpers when Dean twists his left nipple, and then cups his tit with a
firm grip.
Dean’s mind is clouded by the thoughts that are always running through his mind
lately. He wants, no, he needs to breed Sam, to fill him to the brim with cum,
and have his belly growing with their children. He dreams of getting Sam
pregnant, his body would become even more beautiful and Dean would worship
every inch of him, day and night.
As he comes down Sammy’s throat Dean opens his eyes, the sight of Sam, eyes
shut in bliss, fake cock fucking his greedy ass, Dean gets an idea.
 
Dean comes home one day to find his Omega completely naked watching himself in
the mirror. Sammy’s in love with his own body, though he complains from time to
time about not fitting in his pants or having to wear bras to stop his c-cup
tits from bouncing. He’s quite proud of his belly though, it’s not muscled but
it’s flat.
Dean leaves the keys on the table and comes behind Sam, kissing his shoulder
and cupping his tits, playing with pinkish nipples, making them hard between
his fingers.
“Hello, Dean” Sam greets him with a smile, ass rocking backward.
Dean sucks a hickey on the Omega boy’s neck, hips thrusting forward. It’s a too
familiar scene.
“Baby, I’ve been thinking…” Dean begins, peppering Sam’s back with messy wet
kisses.
“Mhhm?”
“We should get you on birth control” As soon as he says it Dean feels Sam’s
smooth body go rigid.
“What?”
“Yes” Dean says, now at full height, eyes locked with Sam’s.
He takes both of Sam’s breasts in his hands and starts to caress them, albeit a
bit harshly.
“The pill will make these perfect tits even bigger, and I know you want them
bigger. You envy those girls with tits so big they hang and make their shirts
look way too small. You’ll have them as big as you ever want and…” Dean stops,
left hand abandoning the softness of the breast to settle between Sam’s thighs.
“And...?” says Sam expectantly.
“I’ll knot you, Sammy. You’ll have your big Alpha brother’s cock knotting your
slutty Omega hole. I can stretch that ass wide, feed my knot to it. It’ll help
you calm down in your heats. So it’s a win-win for you, baby. Bitch tits for a
bitch to be fucked and knotted.”
Sam’s thighs are trembling, his hole producing so much slick it’s embarrassing.
He didn’t think Dean would notice his greed for bigger boobs, it was rare
enough for him to have them this big and he still wanted them to grow bigger.
It was humiliating and exciting to know Dean knew about his fantasies. But
having Dean knowing and supporting him so openly and understandingly made Sam
make his choice without hesitation.
“Yes, let’s get me birth control”
Dean chuckled and grinned like a child who’d gotten his way. Out of his
briefcase he took a small white box. There were 28 little red pills inside.
“Got them on the way back, thought I’d ask nicely first”
Sam rolled his eyes but kissed him anyway.
 
It has been two weeks since Sam started taking his birth control pill and he
can already see changes in his breasts.
They certainly look much fuller and heavier, they ache a little but that’s a
small price to pay for bigger tits, he’s decided.
By the time a month has passed his breasts are definitely at least two cups
larger. He loves staring at them and moving in certain ways to see them bounce
and hang and they’re so squishy. And his nipples are so goddamn sensitive all
the time, he can feel the nubs stiffening when his the clothes so much as brush
against them. From time to time, white little drops will come out of them.
His belly is no longer flat, there’s a pooch that won’t go away, but Dean
doesn’t mind. On the contrary, he seems to be more in love with Sam’s body
every day. Even if his belly is no longer flat, or his tits are exceedingly
big, or his ass is plumper.
Another effect the pill has had on Sam is that he is horny all the time. He
can’t stop touching himself and thinking about Dean and the day when his
brother will knot him properly as the Alpha he is.
He wants to be claimed and mated, he’s only fourteen but god knows it’s way
past time he gets mated.
Dean decides they should move to a bigger place, have at least one room apart
from the living room. So in less than a week they’re carrying boxes with their
belongings to a new apartment. An old man and his younger omega cross paths
with them and their eyes ogle Sam unashamedly.
Sam’s wearing a low cut top, tits about to burst from the strain of keeping
them in such a small piece of cloth. They’re huge, and by no means go
unnoticed. The Omega’s mouth is wide open and the Alpha’s starting to get
closer.
Before he can take another step towards Sam, Dean is already there. He growls
dominantly and the other Alpha steps back. Dean cups Sam’s ass cheek with his
hand and up they go, till they’re inside the apartment, all boxes carried in.
“What was that?” he asks Sam “Did he do anything to you, anything at all?”
there’s concern in his voice but also a hint of …anger?
“No, he didn’t do anything, Dean” replies Sam.
Sam looks so beautiful Dean can’t really blame the guy. Such a young omega,
obviously fertile and unmated, it’s a miracle Sam’s made it this far without
being mated. Then again he almost never leaves the apartment, and Dean’s scent
clings to his body almost all the time.
As he takes a good look at Sam, pouty lips, tits threatening to spill out,
thighs thicker, Dean decides lying to Sam about the pills was the best choice
he’s ever made. The little red devils’ purpose is only to make Sam’s hormone
and fertility levels increase. After all, Dean’s only desire is to breed his
Omega.
 
That night, they both lie naked in bed. Dean’s kissing Sam’s belly, grabbing at
the fat of his sides. He can feel Sam’s body getting warmer, an indication of
his heat arriving earlier than expected. And Dean decides this is the night.
He goes up to suck on Sam’s nipple. He teases the nub with his tongue and then
squeezes the tit in his hand, a tiny amount of hot liquid spilling in his
mouth.
“Are you… lactating, Sammy?”
He can see Sam blushing but the boy nods anyway.
Dean ravishes the nipple in his mouth trying to make more milk come out of it
but nothing does, so he moves on to the other one.
He manages to make a little more of it come it but not nearly enough.
Dean lines himself in order to fuck Sam’s ass, he goes inside in a single
thrust. No previous preparation is needed these days, Sam’s leaking so much
slick it’s unbelievable.
Being inside the tight heat is always the most pleasant sensation Dean’s ever
felt, but this time it’s different. It’s hot and tight, but it’s also unlike
the other times. It’s as if Sam’s ass is nursing on his cock, trying to milk
the cum out of him with intense voracity.
He fucks Sam’s ass imagining his little brother pregnant and riding his cock
like the Omega he was meant to be, Dean’s Omega, belly full of their children,
asking for more and more.
The rim clenches tighter around Dean’s cock, Sammy’s fondling his massive tits,
and the Alpha can feel his knot forming. In less than four thrusts it’s a hard
mass at the base of his cock struggling to get past the Omega’s tight little
wet asshole.
Dean can hear Sam moaning and whimpering and crying and moaning again, and then
his knot is pushed inside the Omega’s ass, cock spilling its seed deep inside
Sam. And then Dean’s biting the side of his neck, properly mating him, cock
still spilling cum inside his hole.
Sam’s ass aches from being stretched so wide. But it feels so deliciously good
he won’t mind if he ends up with a gaping hole for the rest of his life.
Wanting to knock up Sammy has taken over Dean’s life. He lives to please the
Omega now, to fuck him and claim him whenever possible, and Sam… he just takes
it so good, like a good Omega should.
He’s lactating so much his shirts get wet patches on them all the time. Dean
comforts him and suckles on them with indecency, taking in his mouth all he can
fit inside and sucking hard.
At the third month of being on the pill Sam starts to feel a bit heavier and a
lot rounder, this can’t be happening, he’s been taking the pill religiously
every day... He’ll have to tell Dean about this. Sam has no doubt he’s
pregnant.
After fucking lazily, Dean and Sam cuddle with the Alpha as the big spoon. His
cock is deep inside Sammy, locked by his knot. His hand comes to rest to Sam’s
belly and then Sam just… knows.
“Those weren’t birth control pills, were they?”
“Nope” Dean says.
He starts to rock inside Sam once again as he talks again “I’ve been dying to
knock you up, Sammy. To breed so, so good, and get you so pregnant you can’t
even walk without waddling. You’re so beautiful. An Omega like you should be
kept bred all the time and that’s what I’m gonna do. Keep your belly round and
your big titties spilling milk all over. Even your ass tastes sweeter like this
Sam.”
“Oh, Dean… I, don’t know what to say”
As Dean rolls his hips another load of cum paints Sam’s insides and the Omega
sighs blissfully.
“I’ll make you the happiest pregnant Omega in the world, baby. There isn’t
anything sexier than you right now.” His hand draws circles on Sam’s belly.
“I’ll breed you every night, so everyone knows your Alpha’s taking good care of
you. Your body’s mine, Sammy. And I’ll put as many babies in it as I want,
‘cause you’re MY omega. Is that clear?”
Dean’s hand slaps Sam ass and then the Alpha’s fucking him again, tied by the
knot his movements are slower but he gets deeper and deeper inside.
Sam, after much struggling, gets on top of Dean, and rides gracefully the knot,
arching his back and throwing his growing belly forward. His breasts must be
quite a show bouncing pornographically, but as he opens his eyes and looks at
Dean with tenderness they both know Sam’s fate is sealed.
 
Sam is on his eighth month of pregnancy, his belly an incredibly round
projection, his breasts are sore and his nipples hurt almost as much as his
back. An ultrasound revealed he’s carrying quadruplets.
Dean couldn’t be happier.
He kisses Sam’s pregnant belly every day, complimenting him on how beautiful he
looks, and he’s become obsessed with drinking Sam’s milk. He suckles the
Omega’s tits lovingly and plays with them, apparently mesmerized by their size
and their juices.
Sam never thought this would be his life at 15.
He’s riding his brother’s cock, there are four babies growing inside of him,
his breasts are bigger than anyone else’s he’s ever seen and are currently
gushing white streams of milk, and he never ever wants to be anything else than
his Alpha’s breeding Omega. He wants to be kept like this for as long as it’s
possible.
Just as Dean’s knot passes through his rim and the Alpha comes heavily inside
of him, Sam knows he was born to be nothing else than this, and he couldn’t be
happier.
End Notes
     glad to receive prompts~
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