
Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/595021.
  Rating:
      Explicit
  Archive Warning:
      Choose_Not_To_Use_Archive_Warnings, Underage
  Category:
      M/M
  Fandom:
      Sherlock_(TV)
  Relationship:
      Mycroft_Holmes/Sherlock_Holmes
  Character:
      Mycroft_Holmes, Sherlock_Holmes
  Additional Tags:
      Rimming, Anal_Sex, Underage_Sex, Oral_Sex, Sibling_Incest, Dubious
      Consent
  Stats:
      Published: 2012-12-16 Words: 2761
****** Reciprocal Altruism ******
by kirstenlouise
Summary
     Mycroft agrees to do Sherlock's maths homework—for a price. Follow-up
     to Things_Truly_Wicked.
Notes
     Many thanks to the lovely ficklepig as well as the anons who gave me
     some advice on this fic when I was originally trying to bash it out a
     couple of months ago. I would have left it to rot away on my hard-
     drive, forever doomed to be unfinished, without them.
"Mycroft, what's the limit of one hundred over x-squared plus five, going to
infinity?"
"Zero."
He turned the page of his notes, continuing his transcription as Sherlock
resumed his hurried scribbling. It was easy enough to tune out the scratch of
his pen, the sound swallowed up into the background as Mycroft converted his
shorthand to something more legible.
"What about the limit of seven over x-cubed minus twenty? To infinity."
"It's still—" Mycroft glanced up sharply. "Why are you bombarding me with maths
problems?"
"Homework."
Ah, of course. The hated horror of homework. He should have known. Mycroft made
a brief note on his cuff in pencil before turning back to his still sulking
brother.
"I've no intention of doing your homework."
"Not even—"
"No, Sherlock. Now hush. I've no time for your temper tantrums today. I'm quite
busy."
Whatever rejoinder Sherlock had prepared for him came out as a frustrated growl
as he flopped back on Mycroft's bed. As was so often the case, Sherlock
permitted him nearly two consecutive minutes of silence before groaning
melodramatically. Mycroft didn't bother to look away from his notes. Better to
deny him the satisfaction.
The groan sounded a second time, louder and, if possible, even more irritating.
"What is it now, Sherlock? Are you having a fit? Shall I send for a medic?"
With a quiet chuckle, he jotted down another cuff note. It wouldn't do to
forget his little rendezvous later.
"You could do it for me, you know," Sherlock said.
"I could," he agreed, "but I won't. You're perfectly capable of a little simple
calculus."
Mycroft feigned interest in his notes, savoring the huff of frustration
Sherlock failed to hold back. Out of the corner of his eye, he caught Sherlock
rolling off the bed, bare feet silent on the carpet of Mycroft's room. His
hands came down on Mycroft's shoulders a moment later.
"I could make it worth your while." There was no need for Mycroft to turn to
know Sherlock was smirking. It was evident from the tone he'd taken. "Are you
listening, brother?"
"Intently."
"We both know what you were after last Sunday tea." His voice had no right to
be that low or that smooth, Mycroft reflected. Never mind the heat of
Sherlock's thin, clever fingers working loose the knot of his tie. "Punishing
me."
"Mmm. You'd have let me have it, too, you greedy little slut."
The playful dip of his fingers beneath the collar of Mycroft's shirt was
confirmation enough. He nipped at Mycroft's earlobe, more viciously than was
perhaps necessary.
"You spoilt me, you know. Dirtied me up. Ruined me, Mycroft."
"Oh, do let's not be dramatic."
Sherlock's hand withdrew, halting its gentle exploration. Mycroft swiveled to
face him.
"You're not the least bit penitent, are you?"
"You wouldn't find me half as fascinating if I were." He favored the boy with a
smile, privately delighted by the slight widening of his eyes. He dropped his
hand to Sherlock's hip, stroking absently over the sharp lines of his pelvis.
"Well? I was under the impression you wanted to exchange."
He pitied the boy, really. He was already all aflush, his pains to hide it
beneath a veneer of coquettishness notwithstanding. When Sherlock climbed into
his lap, he couldn't help but smile. Sherlock responded in kind, arms twining
about Mycroft's neck to steady himself. He bit his lip, prettily. Such an
obvious affectation should have seemed garish—entirely too artificial to be at
all appealing—but it was a pleasing affectation all the same.
Mycroft slid the pad of his thumb over Sherlock's mouth, catching on one of his
sharp little teeth.
"Go on," he encouraged. "Suck."
Sherlock's face flooded with red for the briefest second before the pink tip of
his tongue flicked out, wet and tentative against Mycroft's thumb. He pushed it
a little deeper, pleased at the utter lack of resistance as Sherlock's mouth
closed softly around the digit. Suction followed moments later, accompanied by
soft, suckling noises that sent his cock swelling.
He slipped his thumb free, gently brushing away the lingering saliva along
Sherlock's bottom lip.
Sherlock batted at his hand. "I can do it myself, Mycroft."
"I've no doubt." He leaned back in his chair and laced his hands over his
abdomen. "I think I'll have you naked now. Eyes on me."
There were few sights more pleasing than the tremulous striptease of a boy
forced to watch you watching him undress. Sherlock performed with stiff-necked
pride, beginning with the buttons of his shirt until he stood bare in front of
Mycroft, naked as the day he was born and infinitely more intriguing. He wasn't
surprised to find Sherlock hard, not at this stage. It was the thrill of
obedience, coupled with the possibility of insubordination; the mild perversion
flavored with a deeper taboo.
Sherlock liked this, even if he was too proud to admit it.
"Closer now, pet."
Sherlock held back, wary. "What for?"
"Don't worry. You'll enjoy yourself, I'm sure."
He caught Sherlock by his soft, slim hips and tugged him forward. It was almost
too easy to flip him round. Sherlock bent over all on his own, arse presented
in vulgar delight. Such a smooth, plump bottom. Sherlock responded with a sharp
intake of breath as Mycroft's hands spread his cheeks wide.
He blew lightly over the exposed hole, eliciting a delicious, full-bodied
quiver. The barest touch of his lips made Sherlock jerk away.
"Mycroft!"
"How did you imagine I'd get you wet enough to take my cock, you silly boy?"
Sherlock sunk back to his former position, aided by Mycroft's hand planted
firmly on the small of his back. Mycroft dove back in immediately, trailing wet
little kisses over his brother's pink little hole and running his hands up and
down the backs of his long, slender thighs. The way Sherlock was responding, he
wouldn't even need his fingers. The flicker of Mycroft's tongue along his cleft
and the light nosing over his perineum were making him unfold without
difficulty.
He spat and Sherlock reared up. "That's revolting, Mycroft."
Mycroft ignored his outburst and pressed him back to the desk. The gob of
saliva was already slicking its way down the curve of Sherlock's arse. Mycroft
spread it with his tongue, licking and laving, harder now. Sherlock wriggled
atop his desk, breathing hard and shaking with every pass of Mycroft's tongue
over his wet little hole. He was so lovely like this. It was a wonder he hadn't
considered it before.
Mycroft used both thumbs to spread his pucker wider. It gave easily under the
pressure of his fingers, exposing a soft, pink centre. He let just the tip of
his tongue slip inside, fighting the urge to smile when Sherlock gave a jerky
press back toward his face. It was almost too easy to sink his thumbs into
Sherlock, both at once.
"You're ready for me now, aren't you?" he remarked, pleased by the ripple down
Sherlock's spine as he fought not to roll his arse into Mycroft's hands. "Ready
to sink back onto my prick. Admit it."
Sherlock's voice was defiant, if breathy. "I hardly need to encourage you."
"Admit it," Mycroft clarified, "or I'll leave you naked and wanting and you'll
have no one but yourself to blame."
There was something greedy about the way the boy immediately pressed back,
trying to take Mycroft's fingers up past the knuckle. The reply followed,
grudgingly. "Just give me your prick, Mycroft."
"Is that how you ask nicely?" He gave a final twist of his thumbs before
withdrawing. Sherlock gave a choked moan. "Don't be insolent. It isn't
becoming."
"And having your fingers jammed up my arse is?"
Mycroft gave him a good smack. "On the bed, little brother."
On shaky legs, Sherlock did as he was bidden. He sat cross-legged on the bed,
his hard little cock jutting up from his lap. Mycroft watched with interest as
he started to play with it with little twists of his hand. His belly was
already sticky—he'd come early on, then.
"I want to see it this time, Mycroft."
"See what, precisely?"
Sherlock glared, pairing the expression with a sharp tug of his cock. "Your
prick, you berk. Last time you only let me feel it."
Mycroft remembered the last time quite well. As well as he remembered the state
of his trousers after. Better to lay them aside this time. He undressed without
fanfare, quickly and efficiently. He had no interest in putting on a show. He
stood at the edge of the bed, letting Sherlock look at him and watching the
boy's Adam's apple bob as he studied Mycroft's prick, half-hard and heavy along
his thigh.
A hand reached out to settle on his belly. Mycroft covered it with his own and
guided it gently between his legs, letting Sherlock's fingers curl into the
wiry hair there before wrapping them around his cock. He let his free hand curl
around the base of Sherlock's neck, pulling him forward a bit.
"Open your mouth."
"You didn't say I was supposed to suck you off." Sherlock's eyes darted off to
the side. Mycroft bumped his cock against his cheek, smearing precome along the
sharp ridge of a cheekbone and bringing a fresh flush to the surface of his
skin. "Knock it off, Mycroft."
"You can suck me now or you can suck me after I've come in you."
"You're revolting."
"We've all of us our flaws. Now be a good boy and open wide."
Sherlock's eyes flashed defiance, but his lips parted enough for Mycroft to
feed him the head of his cock. He didn't need to take more than that. Not
today. Sherlock sucked with his eyes off somewhere to the side. Mycroft let
him. He'd come round, sooner or later. When he was hard he pulled back with a
soft pop, taking a moment to admire the wet shine on Sherlock's mouth and chin
before pressing him back on the bed and spreading his knees.
Sherlock cried out at the shove of his cock, sharp and high enough to shatter
crystal. He grit his teeth and glowered. "That hurt, Mycroft."
"And now it's over," he soothed, running a hand along the boy's cheek. "You
should thank me for not dragging it out."
His little cock had deflated in the interim, but no matter. Boys always went
soft the first time. Mycroft would soon have him stiff again. Sherlock gave
another yelp as he began to move, a slow glide in and out of his snug little
passage. He bent to kiss away Sherlock's scowl, lapping at the seam of his
mouth.
"I'll make you come if you're a very good boy. Would you like that?"
His mouth quivered against Mycroft's, his hips rising ever so slightly. That
was answer enough. Mycroft hooked an arm under Sherlock's back and rolled them
over without breaking contact, folding Sherlock down against his chest. His
back was beading with sweat as Mycroft stroked over the sharp knobs of his
spine, all the way down to where they were joined.
Sherlock was stuffed to bursting, the poor thing. Mycroft massaged his taut
little hole, trying to relax him as he lay sniffling against Mycroft's
shoulder.
Mycroft sucked two fingers into his mouth and wet them liberally before
reaching back down to where he was pressed inside Sherlock. He rubbed lightly
around the rim as Sherlock rocked back and forth in an attempt to work himself
loose. He let a groan of pleasure escape his lips, delighting in the way
Sherlock flushed at his praise. Sherlock kept shifting, his muscles squeezing
Mycroft deliciously as he tried to get comfortable on Mycroft's prick.
Sherlock rubbed his face into Mycroft's shoulder, mumbling, "Why haven't you
come yet?"
"Don't tell me you're bored, little brother."
Sherlock sat back on him with a scowl. "You're just lying there."
"I don't recall complaining when you were too frightened to even shift your
knees apart for me," Mycroft responded mildly. He stroked along Sherlock's
belly, sticky under his fingers. "Are you so horrified by the thought of having
to work for what you want?" Without waiting for an answer, he cupped Sherlock's
cock in his hand. Sherlock's hips twitched forward. "Quid pro quo, brother."
For the longest time, Sherlock only stared, gaze calculating. At the last, he
gave a minor rock of his hips atop Mycroft, as if testing the waters. Mycroft
rubbed his prick encouragingly. He was firming up again quickly. Typical, for a
boy his age. Mycroft wouldn't begrudge him a second climax or even a third, if
he behaved. He liked the sound of that—Sherlock gasping, bucking into his fist,
oversensitized and half-raw from rubbing his little cock against the wood grain
of Mycroft's desk and still unable to help himself from rutting against him.
Sherlock's palms dug into Mycroft's shoulders as he raised himself a few inches
before sinking back down, brow furrowed. His knees rubbed sharply against
Mycroft's sides, his nails bitten and uneven, his movements ungainly and
unpracticed. Perfect. Mycroft drank in the sight of him with his flushed skin
and his slim cock bobbing against his belly. He’d imagined this before, a
hundred times in between now and the afternoon he’d rubbed himself off between
Sherlock’s thighs, but the reality of it was quite different. More thrilling
than he’d imagined, breaking one of the few taboos left to them. He typically
preferred his partners more skilled and better versed in the art of lovemaking,
but it was intriguing to be the teacher for a change—to lie back and simply
luxuriate in the sight and the sensation as Sherlock rode his cock.
"You're enjoying this, aren't you? Despite your best efforts."
"Piss off," Sherlock muttered. His breathlessness dulled the impact somewhat.
As did the fact that Mycroft's jibe hadn't made him slow down a bit. If
anything, his movements were growing increasingly frantic, making it clear that
he wasn’t simply tolerating Mycroft, but actively appreciating the sensation
created by his cock nestled snugly inside him. "You said you'd let me come."
"Am I hindering you in some way?"
"What happened to quid pro quo?"
"Nothing at all. Need I remind you that this was your idea?"
Sherlock grasped his own cock and gave it a sharp tug. Mycroft rewarded his
initiative by gently rolling Sherlock's testicles in his palm. He made a
choking sound, breath catching in his throat. It was incredible, to think that
something so simple could be so utterly gratifying. Sherlock's muscles seized a
final time before he splattered hot ropes of semen over Mycroft’s chest, hatred
be damned.
"I hate you," he said. It stung not at all. There was little force behind it.
At this point, his distaste was merely routine. Expected, but not backed by any
sort of enthusiasm.
Mycroft smiled gently. "Yes, I'm quite certain that you do. On your hands and
knees now, if you would."
He took a moment to admire how red Sherlock was, his hole stretched and
glistening, before sliding back inside. Sherlock let out a muffled cry as
Mycroft began to thrust rapidly in and out, the slap of flesh on flesh
obscenely loud. He was exquisite even from behind. Perhaps even more so, what
with his delicate, bird-boned shoulders and the pronounced notches of his
spine. Mycroft pressed a kiss between his shoulder blades, pinched into a high
peak.
"If I'd known setting you on my prick would make you so pliant, I'd have done
it much sooner. Thinking of all the punishment I've meted out,
ineffectively..." He grunted. "When all along, it was this easy? It's simply
horrifying." His orgasm hit only a moment later, a torrent of heat and ecstasy.
He collapsed onto Sherlock's back with a sigh, cock still buried inside him.
"Have I mentioned how extraordinarily lovely I find you like this?"
Sherlock grumbled underneath him. "I can feel every biscuit you've ever stuffed
your face with."
"Don't ruin the moment."
"You're absolutely the most revolting human being I know. If you are human."
"Regrettably so," Mycroft sighed. He closed his eyes. "It would take a far
better man than I to resist your particular charms, rudimentary and common
though they may be. A far better man than any man I've ever met, perhaps. Would
that I were more than a simple, earthly—"
"Pervert," Sherlock finished. "Deviant, if you prefer, but most definitely some
breed of degenerate."
Mycroft smiled against the back of his neck. "Yes, I love you, too."
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