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Had twenty-two-year-old Mycroft been smarter, he would have pulled Sherlock's door back shut the moment he smelled it.
Instead, he froze in the doorway, his nostrils flaring as he inhaled the scent. Sherlock was an omega. It was rare enough for a beta couple such as their parents to give birth to an alpha, since the gene rarely skipped even one generation. When Mycroft had hit puberty, the family practitioner recommended that Mummy prepare for the possibility of her younger child also being an alpha.
Nobody had thought to prepare for an omega. A glaring oversight, as it now turned out. Nobody in their right mind would have left a suspected omega of Sherlock's age in the care of an unmated alpha, older brother or not, especially since alpha proximity was a not uncommon trigger for an omega's puberty.
“Sherlock?” Mycroft questioned as he stepped into the room and closed the door behind himself. There was no lock, but that was of no consequence, as the house was empty of other occupants and would be for the next five days while Mummy was in a conference. Her current fiancé avoided Sherlock and the house, and would not step a foot in when Mummy wasn't around, and their most recent maid had left a week ago after finding a dissected fox in Sherlock's room. Mummy had yet to replace her; good help was hard to find, nowhere more so than in their household.
“Go away, Mycroft,” Sherlock hissed with a glare that held more pain than anger. He was curled in a ball on his bed, his white shirt soaked through with sweat, sticking to his skinny torso. His black trousers hid it, but the scent permeating the room was strong enough that they must have been equally wet. Mycroft felt drunk with it, his cock hardening and pressing against his trousers.
“Do not be stubborn, brother mine. You must know you cannot go through your first heat without assistance. And we both know how you feel about doctors.”
“I'll manage.”
“Clearly.” Mycroft forced himself not to approach the bed, no matter how much his body urged him to take, fuck, claim. He leaned against the door instead and crossed his arms over his chest. His usually comfortable three-piece suit felt suffocating and hot, but he couldn't undress lest Sherlock draw the wrong conclusions. Or the right ones.
There was nothing he could do to hide the bulge in his trousers, and he didn't bother trying. Sherlock was familiar enough with biology to know how Mycroft's body was bound to react. But Mycroft had always prided himself as an alpha not led by his base desires, and he needed to show restraint in the face of Sherlock's resistance. “Show me then, little brother, how you'll manage.”
Sherlock growled in irritation. Mycroft felt an answering growl build up in his chest, but he clamped down on the noise and on the instincts telling him to put the brat in his place. No, that was not how he wanted this. He could do better than that, could restrain the dominant drive until Sherlock was ready to answer it with willing submission. A show of force may have been the key factor in the choice of mate for omegas before, but humanity no longer lived in caves and hunted for their food. There were more important factors now, and certainly several things both Mycroft and Sherlock valued more highly.
Failing to get a reaction out of Mycroft, Sherlock grimaced and started opening his shirt impatiently. He threw it on the floor and pulled off his trousers and pants, his eyes daring Mycroft to comment. Mycroft kept his expression mild and disinterested with an effort. It was the heat, he knew, Sherlock presenting and his scent morphing into that of an omega; he'd seen Sherlock naked countless of times, the last occasion only a few days ago, and it had never inspired such a reaction in him. But now he could not deny it, even though intellectually he knew Sherlock's body looked the same, scrawny and indecently young.
Fifteen, Mycroft reminded himself, he is fifteen. He felt disgusted with his desires, but that unfortunately made them no less real. He doubted he'd ever see Sherlock the same way he had, even after his heat had passed. Sherlock was delectable. He was aroused, erect and wet between his thighs. His smaller body called for Mycroft to cover it with his own, to touch and hold and mark him.
Sherlock fell back on the bed, curled up on himself, but he reached behind himself and quested his fingers to his slick hole, a small whimper escaping as the tips brushed over the sensitive flesh. Mycroft felt his cock twitch at the sight of the darker skin surrounding Sherlock's hole, looking tight and wet and fuckable. He saw Sherlock brace himself, determined, as he pressed his eyes shut and pushed two fingers inside himself, sliding them easily past the rim with the slick that had gathered there. The angle looked awkward, but even his own fingers were clearly a relief, and the noise he made was obviously unintentional. Fingers were hardly a sufficient substitute for a knot when an omega was in heat, but they would still help somewhat, and Sherlock must have been in agony with his reluctance to see to his body's needs.
Watching Sherlock's fingers disappear in his hole, slide in and out, was like the most delicious torture. Mycroft was achingly hard, had to press his nails into his palms as he stood still by the door. His hips twitched, his whole body geared up to fuck. Sherlock's frustrated, pained expression stirred something possessive inside him, he wanted to touch Sherlock, to give him relief and pleasure, and pain only at his hand. Thankfully, Sherlock's discomfort finally overrode his stubbornness.
“Mycroft,” Sherlock gasped, and that was all the permission he needed to let go of the restraint. He was by the bed in four quick strides.
“Hush, Sherlock, I'll take care of you.”
“Hurts.” Sherlock sounded so young, so vulnerable, it made him shiver.
“I know darling,” he said softly. He felt a strong urge to comfort, which made him feel slightly less wary of himself. Not all his instincts were the twisted sexual urges that were making his blood run hot.
He knelt on the bed and laid his hand over Sherlock's, gently pulling his fingers out of his hole. Sherlock released a pained whimper, which Mycroft hoped to soothe away. He turned Sherlock onto his stomach and crawled on top of him, laying a kiss on his shoulder. Sherlock, although only a few inches shorter than him these days, seemed small below him, thin and fragile even with the wiry muscle on his body. Mycroft's hands looked large, sliding down Sherlock's narrow waist to his hips. “Up on your knees, love, present properly for me.”
Sherlock obeyed without a complaint, seemingly also influenced by his natural instincts, and as soon as he was kneeling, forearms braced against the mattress, Mycroft slid his fingers deep into the wet heat of his body. Sherlock moaned, pushed back into his hand, and Mycroft couldn't help rutting against his brother's thigh as he watched Sherlock's hole accept the intrusion, tight and hot around his fingers.
He traced the contours of Sherlock's back with his other hand, over his spine and shoulders, then leaned down to kiss the back of his neck as he ran his hand across his chest, his other hand still fucking into his brother. Sherlock's scent was heady, seductive, and Mycroft lost himself in it, pressing gentle kisses on the skin, pausing only to inhale deep.
Sherlock's impatient voice startled him back to the present. “It's a heat, Mycroft, it's not your fingers I need. Just do it already.”
Mycroft let out a low growl, scraped his nails across Sherlock's chest, making him release a startled gasp. He kneeled back and took his hands away from Sherlock's body just long enough to get his trousers open and push the undergarments out of the way, then leaned back over Sherlock and guided the tip of his cock to Sherlock's hole, letting it rub over the skin. He could feel the half-formed knot under his palm; this was the problem with waiting. Sherlock's body would help to ease the way, but he knew he'd have to hurt Sherlock to get it in. Sherlock's scent had had an effect on him, made his body respond in the natural way, and being in the presence of an omega in heat for so long had him already on edge, his cock full and throbbing.
“There will be some pain,” he warned, but Sherlock just turned his head in an attempt to glare at him.
“I'm not going to break,” he said derisively. “Just give it to me."
A low growl escaped Mycroft and he sank his teeth into Sherlock's shoulder in warning, a part of him startled by his lack of self-control, another revelling in the way Sherlock whined and lowered his head submissively in reaction. Mycroft licked on the bite mark and then knelt up to watch as he pressed in, gripping Sherlock's hips, his glans sliding easily past Sherlock's slick rim. He couldn't help the moan as he rocked his hips, Sherlock's body allowing him entry, the hot walls of his channel enveloping his cock in tight warmth and the slick of his hole easing the way until his knot was resting against Sherlock's hole. Sherlock's chest was heaving as he panted and moaned, sounding almost incoherent. “More. Mycroft. Please.”
Mycroft growled again, not in warning this time but arousal. He pressed in again, with shallow thrusts of his hips. It took a few tries before his brother's body gave way and his knot stretched the rim and pushed past it, making Sherlock yell out, his knuckles white as he clutched at the bedclothes. Mycroft groaned, his hold tightening on Sherlock's hips as he pushed further, thrusting until his whole knot was sheathed in Sherlock's tight heat and he was buried to the hilt.
Sherlock's body shook with sobs that made arousal burn in his veins. He covered Sherlock's body with his own, rocked into him with quick, shallow thrusts. Even with his knot only half formed Sherlock felt impossibly tight around him, his knot allowing only the slightest movement, but that was enough, made hot pleasure gather low in his stomach.
Despite the pain Sherlock was in, his body was responding to being knotted, and the waves of pheromones made Mycroft feel as if he was high. He could feel his knot swell as he thrust into Sherlock, his mouth tracing Sherlock's shoulders, biting down, licking up Sherlock's neck where the scent was the strongest. He was careful not to bite there, even in the height of his desire sober enough to realise that bonding would bring with it a sleigh of complications neither of them was prepared for. But he couldn't resist leaving his marks elsewhere on Sherlock's skin, especially once Sherlock's pained whimpers begun to turn into moans of pleasure. Had Mycroft not been so out of it, he would have felt shamed by his desire to hear the sounds of pain from Sherlock, but as it was they simply spurred him on, made him rock into Sherlock faster, harder. He braced himself on one arm, his other hand gripping Sherlock's hip tight, pulling him closer as he thrust in, until he felt the pooling heat surge and implode, his knot swelling and locking them together as he erupted, white-hot shocks of pleasure making his vision blur, making him moan as Sherlock's muscles tightened around him, milking his seed out of him. He leaned heavily over Sherlock and rode out the waves of pleasure, panted in his brother's increasingly heady scent as he filled him up.
“Mycroft.” Sherlock sounded needy and frustrated, although not as desperate as before, not now that he was knotted. His hips were twitching in small, aborted movements. It seemed he was unable to find release from knotting alone – although he would learn, some part of Mycroft's brain interjected – and his arms were pinned under their combined weight.
Mycroft took some of his weight off Sherlock and loosened his grip, a warm satisfaction blooming inside him to see the reddened skin and nail marks he'd left on his brother's hip. He reached around Sherlock's waist and palmed his erection, his hand nearly large enough to fully cover Sherlock's cock. Sherlock whimpered and rocked instinctively into the touch, moaning in pain as the knot jarred inside him.
“Patience, brother,” Mycroft chided, but he tightened his fingers around Sherlock's cock and moved his hand from tip to base. Sherlock was leaking so much it allowed Mycroft to set a fast pace, jerking him off quickly, and he had Sherlock moaning out his pleasure in mere moments, spilling over his bedsheets and Mycroft's fingers. Mycroft lifted his hand to his mouth to taste Sherlock's come before offering his fingers to Sherlock, shivering as the warm mouth closed around them willingly, licking them clean. Sherlock must have been feeling confused, for Mycroft doubted he was as well-informed about the sexual instincts of alphas and omegas as Mycroft was. It made him wonder if Sherlock understood the meaning of the pressure in his groin that he must have been feeling by now.
Mycroft pulled his fingers out of the wet heat of Sherlock's mouth and slid his hand down across Sherlock's chest, unable to resist a fondle of his soft cock, taking satisfaction in rubbing the rest of Sherlock's come on his skin. Mycroft was still hard inside him, the knot would take up to half an hour to retract, but even then he was unlikely to lose his erection fully after merely one knotting. It would likely not take Sherlock long to get hard again, either, once he had fully submitted. Mycroft pressed lightly on the bottom of his belly and Sherlock released a pained noise, but he was clearly resisting it.
“Sherlock. You need to let go.”
“No. I can't, I'll-- I'll wet myself. Mycroft, don't make me.”
Mycroft made a soothing sound at Sherlock's distress. “There is nothing I can do. You need not feel embarrassed, it is a biological response.”
“I'm not embarrassed,” Sherlock growled, but Mycroft could still feel his tense abdominal muscles under his palm.
“Unless you relax, it will be more uncomfortable than it needs to.”
“Shut up, shut up.”
Mycroft subsided. If Sherlock chose to be stubborn, there was nothing to be done. He left his palm on Sherlock's stomach, moved his other hand in a slow caress over Sherlock's side and up to his neck, sinking his fingers in Sherlock's black curls. He leaned in to smell Sherlock's neck, which was misguided, for his lips parted without his permission and each open-mouthed inhale strengthened the urge to sink his teeth in and bite until he'd feel the bond form.
“You can't actually be considering that.” Sherlock's voice, fascinated and needy and terrified, snapped him out of it, made him rear back.
“Fuck.” Mycroft felt shaken to his core, staring at Sherlock's skin, his breathing heavy and fast.
“You-- you're my brother.”
“I'm aware,” Mycroft snapped. His heart was pounding in his chest. He needed to get away from Sherlock before he did something they'd both regret. He needed to think, clear-headed, needed to gather himself and stay away from his brother until he could trust himself. It was bad enough already, what he'd done, without adding to it, violating his brother's body and soul by bonding with him, by making Sherlock his, permanently...
Sherlock was not the first omega he'd taken. The urge to bite had been there, of course, but he'd never wanted the bond. He'd never craved to possess, to own somebody. Not like some part of him undeniably wanted Sherlock. Mycroft still had his knot inside him, and yet he already wanted to take him again, wanted to have him, wanted nobody else to have him, ever.
Mycroft was startled out of the spiral of thoughts and messy, confusing emotions by Sherlock's moan. He could feel it under his palm, Sherlock relaxing, and he moved his hand lower, cradling Sherlock's penis to feel it as Sherlock finally let go. The stream of piss dripped wet and warm over his skin, and the smell was in no way revolting, it felt right, Sherlock's submission making him feel satisfied on a bone-deep level.
“Good boy.”
Sherlock growled, but it lacked heat. He was loose and relaxed under Mycroft, hardly even protested when Mycroft rubbed his hand over his chest, getting the smell of urine all over him.
Mycroft wrapped an arm around Sherlock and curled above him. His muscles were straining to hold them both up, but lying down felt unthinkable and he had no energy left for fighting his irrational instincts. He pushed his face into Sherlock's neck and breathed in, allowing Sherlock's heartbeat to calm him down.
Sherlock was silent for a while, other than a whimper when Mycroft's knot finally released them and he pulled out. Mycroft was still nearly all the way hard, and he could feel his arousal surge as he watched his seed drip out of Sherlock's hole. His fingers moved without a conscious choice, dipping in Sherlock's hole, but that caused Sherlock to scramble away with an irritated noise. Mycroft didn't try to stop him, simply sat back and watched Sherlock move up on the bed, face Mycroft leaning his back against the headboard, and bring his knees to his chest, likely in part to hide his renewed erection which Mycroft caught a glimpse of.
Sherlock glared at him. “Haven't you had enough yet?”
Mycroft gave a languid shrug. “Neither of us have.”
Sherlock scowled, but didn't contradict the fact. “So what now?” he demanded instead. “This is how it's going to be four times a year? I'll go into a heat so I'll just bend over and have my lazy, stupid brother fuck me?”
Mycroft barely kept from flinching at Sherlock's crudeness. He breathed out and replied steadily, “As long as you don't purposefully ignore the signs of a heat next time, you'll be perfectly capable of choosing a partner yourself. I'm certain you'll have no trouble finding an alpha who's more than willing to oblige.”
“As if you'd let me,” Sherlock said. “Look at you, you can barely get the words out. Don't deny it, you wanted to bite me, wanted to make us bond, so that you could control me and have me to yourself.”
“Instinct.”
Sherlock snorted derisively. “You're such a coward, brother mine. At least I'm observing all of this objectively.”
Mycroft held his tongue with difficulty. Sherlock was brilliant at getting him riled up, but he did not want to use the previous moments of vulnerability and confusion against Sherlock. Instead he responded mildly, “My feelings are hardly relevant. And I shall be in London during your next heat regardless.”
Sherlock's eyes flashed and his lips twisted into something resembling a smile. “Oh, but it does matter how you feel. Just tell me you won't mind, in three months' time, that it won't be killing you to know that while you're attempting to kiss ass your way up in ranks at work I'll be spreading my legs for another alpha. Perhaps the one in my class, he may be stupid but he's also well built, so I'm sure he'd get the job done. I'll let him mount me right there behind the school when we're supposed to be in class when anybody could walk in on us, and he'll have me stretched around his knot instead of you--”
Mycroft palm pressed over Sherlock's mouth, muffling his voice, Sherlock's wide, startled eyes staring at him. He hadn't even registered moving, but he was atop of Sherlock, his other hand trapping his wrists over his head, growling low in his throat, an animal sound he couldn't have held in if he'd tried. He kicked Sherlock's legs open, his hips pushing into Sherlock's, his weight trapping him against the bed, making his attempts to free himself futile.
“You're mine.” He was burning with the need to claim Sherlock, not a mere craving this time but an uncontrollable urge. The rational voice had shut down, he was driven by animal instinct which was pushing him to still Sherlock's struggle and to demand submission. He rubbed himself between Sherlock's legs, his cock sliding in the crease of his arse, and he tilted his hips, angling them right so that the head of his cock was pushing against Sherlock's rim. He thrust, uncaring of the resistance, pressed past the tight ring of muscle and buried himself inside his brother.
Sherlock had stopped struggling and welcomed Mycroft inside him, his mewls muffled by Mycroft's palm. Mycroft let go, keeping his wrists still trapped but moving his other hand from Sherlock's mouth to his throat, pressing lightly, possessive arousal making him shiver as Sherlock panted for breath.
“Mycroft,” he gasped, his eyes still wide, voice breaking as Mycroft fucked into him in sharp, harsh thrusts.
“Mine.” Some part of him realised that he was going too far, but he was too out of control to stop himself.
“Yes,” Sherlock groaned. “Yes, yes.”
Sherlock bared his neck, and Mycroft growled, felt his knot starting to swell inside Sherlock. He buried his face in the pale expanse of skin, mouthed along Sherlock's throat to breathe in his scent, tasting it, open-mouthed kisses all over his throat, his thumb tracing Sherlock's windpipe, making him feel high on power. His blood was rushing in his ears, Sherlock's moans at the thrusts spiking his arousal, making his whole body strain until he finally sunk his teeth into the flesh under his mouth, clamping down at the side of Sherlock's throat.
Sherlock yelled out in pain and bliss, his muscles clamping tight around Mycroft's cock and warm splatters of come spilling between them. But what pushed Mycroft over the edge was tasting Sherlock as the bond formed and flooded Sherlock's body with hormones. He moaned against Sherlock's neck as he thrust in him, his knot swelling to lock them together and he was coming, filling Sherlock's tight ass with his seed and tasting him as waves of pleasure washed over him, making him clutch Sherlock's wrists harder to ground himself.
He only unlatched his teeth from Sherlock's skin when he could feel the bond settle in his body, in his blood, the sense of Sherlock as his mate, as irrevocable as the sense of Sherlock as his brother.
Sherlock whimpered brokenly, and Mycroft could see the red, angry mark. He licked over it, moaning and shivering with aftershocks as Sherlock made a pained sound. It would bruise and scar and nothing would erase it for as long as they lived.
Mycroft closed his eyes, breathing heavily, and tried to find equilibrium as the haze finally begun to lift. He could feel warm wetness spread between them and smell the urine as Sherlock wet himself, letting go much quicker this time. The pleasure, the sense of satisfaction was overwhelming, and he pushed aside the welling panic. He had no time for it now; it was too late in any case. They were bonded. Stupid, irresponsible, yet true. He couldn't focus on that, so he concentrated on the feelings in his body, the heaviness of his muscles, the tightness of Sherlock's body around his knot, the heady rush of hormones and the smell of sex and Sherlock's scent surrounding them.
“This is what you wished to accomplish, I hope,” he said, when he was finally able to form a coherent sentence.
Sherlock sputtered in response, trying to free his wrists and twist out from underneath him, but only managing to glare at him indignantly. “I'm not the one who lost control.”
“And who is being a coward now, brother mine?”
“What would you have had me do?”
“You do understand this means you'll have to come to London with me,” Mycroft said, dodging Sherlock's question. He dreaded the thought of Sherlock living in his house. It would be chaos in his physical space, not to mention the inconvenience to his work. It couldn't be helped, however.
“Better you than somebody else,” Sherlock muttered. He looked at Mycroft imploringly, sounding immeasurably young as he asked, “What are we going to say to Mummy?”
“That is something I have no wish to discuss while in bed with you.”
“But--”
“That's enough, Sherlock. I'll take care of it.”
That made Sherlock subside. He knew that if Mycroft said so, he would follow through. He would make up convincing enough a lie. Thankfully, being a beta Mummy would be unable to smell that Sherlock was an omega or notice that they were bonded. As long as Sherlock was kept away from the few alpha or omega acquaintances Mummy had, they could keep it under wraps for the time being. At work, people would of course be able to tell that Mycroft was recently bonded, and the rumours would circulate, but that would have its advantages for his status.
“You could have the decency to wait until your cock isn't inside me anymore before you start planning your next meal, or whatever you're thinking about, Mycroft.”
Mycroft sighed. “Must you be so crude?”
“Must you be so condescending?” Sherlock retorted, but when Mycroft refused to rise to the bait, they fell into a silence.
Eventually, Mycroft's knot released them and his softened cock slipped out of Sherlock, who winced. Mycroft lay on the bed and rolled Sherlock onto his side, spooning him from behind, unbothered by his protests.
“In less than half an hour, I will most likely need to take you once more, little brother. I'd prefer the easy access.” Mycroft was pleased when that rendered his brother quiet. He curled around Sherlock, face against Sherlock's neck, feeling a warmth in his belly as he kissed the mark. His mark.
Sherlock would be an inconvenience. He would be irritating and messy and petulant. And yet, Mycroft couldn't bring himself to regret a thing.