Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/4253952.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      M/M
  Fandom:
      Gravity_Falls
  Relationship:
      Dipper_Pines/Grunkle_Stan_|_Stanley_"Stanford"_Pines, Stanford_Pines/
      Stanley_Pines, Trash_Ship_-_Relationship
  Additional Tags:
      Sexual_Fantasy, Masturbation, incestual_thoughts, Implied_Twincest,
      Twincest, Switch!Dipper, Switch!Stan, Light_Bondage, Like_super_light,
      HUGE_Age_Gaps, Underage_-_Freeform, Someone_needs_to_stop_me, i'm_total
      trash, Sorry_Not_Sorry
  Series:
      Part 2 of The_Trash_Ship_Collection
  Stats:
      Published: 2015-07-02 Words: 2011
****** Once a Sinner ******
by paranoiapersonified
Summary
     Stan wakes in the middle of the night with memories of his brother
     and some very, very dangerous thoughts of his great nephew on his
     mind.
     Please read the tags!!
Notes
     Oh god, okay, more of the Trash Ship. This isn't the oneshot I
     thought I was going to write (which I still might do anyway, eh). In
     fact, I wrote all of this in one night in a feverish haze because oh
     my god, switch!Dipper. I don't ... I can't even begin to apologize
     for this, I don't feel sorry at all, oh man. ((Although I do feel a
     little worse knowing that it's basically been confirmed that Grunkle
     Stan is actually Grandpa Stan, whoops.))
     This is sort of in the same world as Only the Worst Kind. You can
     choose to view it as a prequel if you'd like, but it can also just be
     a stand alone story. No need to read Only the Worst Kind first,
     although if you like this, you might want to check it out too.
     Enjoy. We're all trash.
See the end of the work for more notes
Stan lays back on his bed. This isn't something he normally had to do—isn't
something he normally wants to do—but the dream left him with a deep,
unsettling ache, stirring so deep and so strong, it was impossible to ignore.
He bites his lip as he takes himself in hand, eyes flitting to the his unlocked
door—there was usually never reason to lock it—and prays that tonight is like
every other night, that no wandering child comes knocking on his door.
The dream is still vivid, burning behind his eyelids. He closes his eyes and
allows his imagination to take him back almost 70 years. His brother had been
rocking against him, clambered over him on Stanford's old bed. It isn't really
a memory, but it isn't quite fictional either. It was set too early, though,
they were too young. Behind Stanford's eyes was a 12 year old, awkward and
uneasy about the way his hips rolled, about the way his nails dug into
Stanford's bright blue sheets.
Stan groans, soft and quiet, thoughts jumping to the actual memory, only four
years later, when Stanley had been far more forceful, hips snapping with a
careful and precise efficiency. God, Stanford had lasted all of a mortifying
two minutes before coming in his own briefs. He hadn't even had skin contact,
just the perfect friction of the soft cotton, the sight of sweat dripping down
Stanley's neck, the gentle tug of Stanford's teeth on his own lip.
But he doesn't linger too long on the memory, the broad shoulders and long,
lean legs revert back to noodly limbs, bony, narrow joints.
Stan runs his thumb over the tip swirling some precum over his sensitivb
foreskin, and he has to bite his lip hard to keep from moaning. He had been the
same age as Stanley in the dream, but his memory of that age are fuzzy with the
dirty lens of decades. He tries to remember what his body felt like then, how
narrow his hips were, how awkward his own arms felt, but it slowly slips in and
out. His small, smooth stomach—so thin you could see his hipbones like roots
peeking out below the dirt—is replaced with his current one, gray and dark
dusting of hair and the soft padding of flab hiding the strong muscles he's
been proud to keep. He hands, tangled fast and firm in the sheets, grow strong
and calloused and knobby. Stanley's delicate legs have to spread wider to fit
around Stanford's thighs. In the fantasy, Stanley moans as he shakily presses
harder against Stanford's now full grown erection, which Stanford generously
rolls back hard against the child.
Stan's hips—his real ones—snap up to meet his downstroke, mouth now open and
gulping down air like there wasn't enough. He runs his shaky fingers through
his sweat-damp hair at the thought of Stanley's small cry. His thoughts run
rampant, suddenly unable to focus on just one thought. He imagines flipping
Stanley over, rutting mercilessly into the boy until he's the one cumming into
his underwear with Stanford's name on his lips. He imagines his tongue dragging
over every inch of the smooth, unmarred skin, tracing trough and tasting the
sweat on his neck, his chest. He imagines taking him in his mouth, still small
and thin, so that he wouldn't even have to use his throat to fit all of him in
his mouth.
The taste of Stanley is something he'll never forget—has never forgotten in 60
odd years—salty and bitter and still somehow sweet and perfectly Stanley
through and through. He accidentally lets a groan slip through his teeth at the
thought of dragging an orgasm out of Stanley, not letting up until the last of
the tremors were finished with him and Stanley would have to plead for Stanford
to stop dragging his tongue over his oversensitized tip, tonguing at the slit
to get at more of that wonderful taste.
"Fuck!" Stan whines, hips jutting in time now with his hand, pace quickening.
Oh god, the things he could do now, the things he's learned over the years,
that he was too shy, too uncertain, to try when they were young. He wishes he
had known, known it wasn't just him, known he wasn't some monster for the
thoughts in his head, for the things he wanted to do with Stanley—do to
Stanley. He had hated himself for years, so afraid and so lonely, not being
able to go to his brother for help.
His mind wanders close to the first time Stanford had touched Stanley, edging
quietly and quickly, as if treading on dangerous ground—like imagining sucking
off his 12 year old twin wasn't dangerous enough—when suddenly it flips. An
accident, truly. Some innocuous, fleeting thought interrupts quietly, reminding
him that he needed to buy some more of that cereal Dipper likes. Something
small. Purely innocent, utterly unrelated to hand on his cock and the harshness
of his breath. But his train of thought is derailed. Derailed horrifically. It
skids of the tracks, screeching terribly as it barrels uncontrollably into
truly dangerous—utterly perilous—territory.
Like how similar Dipper is to Stanley when he was that age. How identically
their habits—idly chewing on pens, chasing blindly after the
supernatural—matched up. How even their bodies looked the same, scrawny arms
and thin chest with the perfect shade of lush pink dusting their shoulders when
they got embarrassed or bothered ... or aroused.
Oh no. No. No. No.
Stan's hand freezes, body deathly still, as he tries desperately to block the
thought. But this derailed train has no breaks, and his mind is mashing the two
together, imagination supplying whatever his own memory lacks. What Stanley
looks like flushed with arousal quickly becomes Dipper's face, burning bright
red with heat, bright brown eyes lidded and unfocused, mouth open just
slightly, just enough to see the wet pink of his tongue peeking out. His chest
heaves with the soft pants and gasps, and Stan can't stop the ungodly heat that
spreads like wildfire through him—from his neck, down his arms, to his toes,
blazing through his chest and coiling tight and white hot just below his
stomach. Within seconds he is on fire with fierce need and icy, chilling fear
blended together in some terrifying, potent thrill. He can feel his heart
hammering in his chest, and it feels like all of the air drained from the room,
his labored breathing can't seem to get any actual oxygen.
Carefully, apprehensively, he moves his hand down his cock in a slow motion.
Then back up, all the way past the tip (the image changes subtly—Dipper's head
tossed back, whine breaking high in his throat). Back down again. Up again
(this time Dip's hands touch gently, cautiously, over his chest, fingertips
just barely grazing his skin, over his collarbone, down his pec, dusting shyly
over his nipples). And back down (they roam lower, down over his stomach, where
he lets out an embarrassed, squeaky huff, tickled by his own touch, until they
rest, almost teasing—but too innocently, too naively—just above his pelvis).
Stan bites his lip, eyes screwed shut tightly, as he begins again, the
swirling, thrilling mass of nerves inside him unsure whether to be pleased or
horrified.
But his imagination takes no time in assaulting him with fresh fuel for the
fire, thoughts of Dipper apprehensively taking his own member in hand, chewing
on his lip as his delicately pleased himself, of Dipper straddled wide across
Stan's thighs, of his lips soft against his own, his deceptively soft curls and
how they would feel under his hands, through his fingers.
His mind settles on the thought of what Dipper's small erection would feel like
in Stanford's palm, slicked slightly with sweat and a little bit of spit. He
doesn't know for certain—thank god—what Dipper looks like naked. At first he
picture's Stanley's erection, somewhat thin, curled almost imperceptibly to the
left, foreskin thick around the head, but it changed little by little. Slightly
thicker, circumsized with a heavy red head that was still sensitive, and pebbly
veins that danced along the underside. Dipper would have to bite his lip when
Stan traced his thumb along those veins, pressing in with just enough pressure
to make the nerves sing. He'd gasp, mouth open in a silent cry when Stan sets a
relentless pace, twisting his wrist with every stroke. He'd have to cover his
mouth, want to hide his face from Stan, as he'd cry out, high and long.
Subconsciously, his own hand begins to match his fantasy stroke for stroke. He
is so close, so, so close, the ragged heat is boiling right beneath his skin.
He has to cover his mouth with his free hand to keep from moaning too loud,
muffling it with his palm first, then his fingers, stroking down his tongue,
dancing at the back of his throat. God, he is almost there ...
A half-thought comes to him abruptly that almost trips him up, hand faltering
on a downward motion. What if Dipper were like his grandpa? What if he got off
on being in control, too?
A long groan—too loud, shit—makes its way past Stan's lips, his fingers, at the
thought. Oh god, what if Dipper were a switch? His mind is flooded with frantic
memories of Stanley, of the rope—oh god, the ropes—of being held down by strong
hands, touched lightly, of being teased and near-tortured with desire. The
thoughts converge, forming a new scene, with Stan on the ground, Dipper
standing in front of him. Stan's arms are bound now behind his back, tied with
a length of rope that wraps up and down his forearms, securing him in place.
Dipper smiles behind his fingers, idly chewing on his nails, and Stan drags his
tongue up the length of him, a flush across his cheeks and pupils blown wide,
eyes bright with want, but otherwise collected. He takes a step back, just out
of reach now from where Stan was sitting on the ground, and takes himself in
hand, stroking languidly.
Stan bites his knuckle hard enough that he tastes blood. He is almost there, he
just needs ... just needs ... just a bit more ...
Dipper moans, and Stan glances up to see his eyes closed and eyebrows furrowed,
hand inches from his mouth with the smallest thread of drool trailing from his
pink lips to his knuckle. Stan groans, and Dipper moans again, eyes opening to
look down at him. He smiles, wide and toothy, almost menacing, and brings his
foot up to Stan shoulder, pressing just hard enough to tilt Stan back, keeps
going up Stan feels himself threaten to topple back. His hand is still moving
on his cock, and he opens his mouth in a soft moan. He leans in close, using
his foothold on Stan's shoulder so that Stan has to brace himself carefully,
hand slowing as he guides himself toward Stan's mouth.
Stan has to cover his mouth, completely unable to stop the moan that tears past
his lips as he comes all over his hand and stomach, back arcing up off the bed
and toes curling into the the sheets, but his hand doesn't stop stroking him,
riding out the waves of pleasure that bleed down his spine. Finally, finally,
his body drains, flopping back down against the bed. His breath is feels raw
against his throat, ragged and uneven, every gasp and pant biting. He drops his
hand, and idly hopes that he managed to stay quiet enough that the twins heard
none of that. He feels a small trickle of ice cold fear that he wasn't, that
they possibly heard him come, but his body is so otherwise relaxed—eyes
beginning to droop heavily again, not one muscle in his body tense—that he
manages not to care for right now.
Stan slowly drifts back to sleep.
End Notes
     If there are any typos or if you find the tone a bit weird, I'm
     sorry, it's 4am and I need to be awake in two and a half hours. I'll
     most likely go back and edit as I see fit. Thank you for reading.
     Just for your information, Stanley is totally a switch in Only the
     Worst Kind. Just saying.
     Feel free to suggest Trash Ship stuff if you want to see more, I'm
     totally open to ideas. Doesn't even have to be nsfw, I like them
     being cute, too.
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