Derek gets back in from his patrol with Scott at two in the morning, sighing as he walks through the front door of the house that he shares with Laura and more often than not, Stiles. It’s late and he’s exhausted and wants nothing more than a shower and maybe whatever leftovers they’ve got in the fridge. He’s halfway into the room before he freezes, blinking at the sight of Laura perched on Stiles’ lap, the flowy, silvery skirt she’d gotten herself as a present spread over their laps like a quilt. Her back is pressed up against his chest and to some people it might look like she’s just using him as a chair. Possibly. But she’s got a flush of color high on her cheekbones and Stiles’ eyes are wide and shock-stupid the way they get when there’s an impending orgasm in the equation, and while she might have an excellent poker face, Stiles really doesn’t.
“You are fooling absolutely no one,” Derek tells them. He pauses, considers. “Probably not even the humans.”
Laura’s poker face shatters and she grins at him, wicked and sharp like silver and fangs. Stiles’ mouth drops open in a soundless moan when she rolls her hips, steady and languid, like she has all the time in the world. He wonders if she’d ordered him to keep quiet. Probably, knowing her. Derek blinks at them, sees the challenging look in Laura’s eyes, and sits down to watch.
“Fuck,” Stiles groans, squirming beneath her. “I cannot do this, Laura. I thought I could, but I can’t. Kill me now, just please, if you love me, don’t let Derek watch.”
Derek thinks about being offended, he really does. But it’s been two years since they brought him back to life. A year and seven months since he’d had Stiles for the first time, in a dank cave that smelt of reptile and mold, under the pretense of fixing their communication problems. By now, he knows what Stiles is like, and even if he didn’t, Stiles would have put an end to that pretty quickly because he goes on to say, “No, seriously. I will probably combust from the hot. I will go boom and then you will only have one second to boss around like the nnngh—”
As he talks, Laura shifts around — giving up the silly pretense of perching daintily in his lap, like she’s not sitting on his cock — and straddling him easily before sinking back down. Stiles cuts himself off with a sharp moan, throwing his head back and making a space for her teeth. He watches Laura’s teeth come down on pale skin, the little human indents that they leave behind.
He licks his lips and thinks about getting his dick out. When Laura starts riding him in earnest, using the couch behind them to brace herself, he says fuck it, and reaches for his zipper.
He watches them for a little while, soaking in the smelltastefeel of the room — the little glances that Stiles keeps sending him over her shoulder, eyes flaring gold, how Laura’s moaning loud, obscene, and obnoxiously pornographic, obviously putting on a show. It sends a flare of heat spiraling down his spine before he even gets his fingers around his dick.
They’ve been doing this awhile, he’s pretty sure. Stiles and Laura. He doesn’t know if the others are aware of it, but he can smell it on them both, Stiles crawling into Derek’s bed still smelling like Laura — it drives him absolutely insane.
He doesn’t know when it started either, just that it was after him and Stiles started whatever it is they have between them. He and Stiles, they aren’t dating. They aren’t, no matter what Erica says. They fight and fuck and save each others lives, and that would be all there is to it, if it wasn’t for how exclusive they’ve been about it. They fuck each other and until Laura, they were pretty monogamous about it.
Derek’s not stupid. He knows that they bonded while he was, well, dead. Laura filled the void he left behind with Stiles and even if turning him was an accident, he knows that if he asked her, she’d tell him it was the best mistake she ever made. So there was a bond between them, this huge, lingering what-if that nobody talked about. He saw how close they were, but until that first night that Stiles had crawled into his bed, smelling like Laura and spunk and sex, and carefully nosed a question into his collarbone, he hadn’t even considered that there might have been something more than pack between them.
He’d been weird about it for a week, allowing Stiles to cuddle into his arms but refusing to actually instigate anything sexual. It was uncomfortable and they’d both probably reeked of misery, because Laura had come to him, swatted him around the head, and said her first and last words on the matter. “Don’t be a jackass, Derek. Just because I’m fucking him doesn’t mean you have to stop.”
And that was that. Stiles had knocked sheepishly on his door that night and Derek had reeled him in by the collar, kissing him harshly, and fucking him against a wall until he’d howled loudly enough that every wolf in Beacon Hills had probably heard them.
It was a weird back and forth — sharing Stiles. The house that Laura bought was big enough that pack sleepovers weren’t an issue, but it wasn’t very soundproof. He’d lay awake at night sometimes, pretending that he wasn’t listening to the way Laura said Stiles’ name when she was coming. In the morning, they pretended that they hadn’t heard him jacking off, so it worked.
His sister is beautiful like this, sweat dotted across her chest and throat, lips open on the jagged edge of a moan or a whimper. The fact that they’re both still dressed, just her panties still caught around one ankle and Stiles’ jeans unzipped far enough to get his dick out is both hot and frustrating. He watches the silky material bunch around her thighs and wants to pull it off with his teeth, wants to tear Stiles’ jeans off of him so he can see where they’re joined together.
He bites down on his lip, hips bucking up into his fist, and the smell of blood fills the air.
On cue, they both glance over at him. He doesn’t know what he looks like right this second, dick in hand and what’s probably an embarrassingly open expression on his face, but whatever he looks like, it’s clearly good, because they both jerk against each other and share this look, like—
Laura climbs off of Stiles again, shushing his protests by sinking back down on him the way she’d been before, her back to his chest. She catches Derek's eyes, and arches a sculpted brow in his direction, then very pointedly, spreads her legs wider. He blinks, watching numbly as she takes the material of her skirt and pulls it back, making it bunch up around her hips. His eyes are helplessly drawn away from her hands on her skirt and back between her legs, where Stiles’ cock is buried inside of her, flushed red at the root.
He isn’t wearing a condom, but then, Derek hadn’t really been expecting him to. They’d both asked him some rather probing, completely unsubtle questions lately about his opinion on children. They always have been transparent.
Stiles groans again, and when Derek jerks his head back up, away from where they’re joined together, they’re both watching him with dark eyes.
“Derek,” his sister whispers, fingers flexing against Stiles’ knee. She jerks her head the same way she did when they were kids, when she’d roll her eyes and make that same motion, the unspoken ‘get your ass over here or get beat’ obvious.
He doesn’t hesitate, crossing the space between them with a few heavy steps, his dick slapping awkwardly against his stomach and then he’s kneeling down and burying his face between Laura’s legs, lapping at the space where they’re joined with broad, helpless strokes of his tongue.
They taste salty and bitter together, like sweat and pre-come and them. Stiles jerks when Derek traces his tongue around the root of his dick, bucking up into Laura with a mewl that she quiets with a small growl. Derek smirks, letting go of his own cock so he can dig his fingers into the pale undersides of Laura’s thighs, spreading them even wider so he can push his whole face up against them, nose grinding up against her clit even as he pushes his tongue right up into her, right next to Stiles’ dick. He can’t get very far, but the quiet, breathless noise that Laura makes as she rocks down onto his face is worth the way his tongue is already cramping up.
He eats her out slowly, filthy and enthusiastic, getting her and Stiles’ good and wet. He makes sure they stay still, holding Laura down even as she growls at him, both of them getting more and more desperate, the longer he spends with his tongue between their spread legs.
“Derek, I swear to fuck,” she finally growls, and he starts, tongue slipping out of her, because that’s her alpha voice and she—
She is completely wrecked, he realizes when he glances up at both of them from under his lashes. Her cheeks are flushed a bright red, lips swollen and hair mussed like Stiles’ has been running his hands through it while Derek wasn’t looking. She’s got this glazed, half-wild look in her eyes, which are gleaming red like an order and a request. He hesitates, looking to Stiles, who doesn’t look like he’s going to be much help. If anything, he’s worse than Laura, flushed that blotchy red that he only gets when he’s really into something, pupils dilated so much that there’s only a very, very thin ring of glowing gold. His mouth is open and wet, panting openly.
Laura is clearly trying to calm herself, because it takes a moment where her mouth moves soundlessly before she grinds out, “If you don’t get inside of me in ten seconds I am going to claw open your stomach and laugh at the pile of viscera.”
“What is with you Hales and all the threats?” Stiles gasps out incredulously, but he looks like he’s not even hearing what he’s saying, trying to buck up and growling when Derek keeps them both firmly pinned to the couch.
His dick twitches and he’d like to say that he has a second where he doesn’t know what Laura’s talking about, but she’s sloppy and stretched all around Stiles, one leg hooked over Derek’s shoulder and the way she’s twitching up, like she wants him back inside her, is more telling than any verbal answer could ever be.
He doesn’t ask her if she’s sure, but he does take the moment to slide two fingers inside her, tapping them against Stiles’ dick just to make him choke on a laugh. Just because he knows that she’d heal if he accidentally ripped something doesn’t mean that he wants this to be anything less than a completely amazing experience for her.
He manages to get another two fingers hooked inside her before she loses her temper and sinks her claws into his shoulders, leaving pinprick holes in the henley he’s still wearing.
Gently, he draws his fingers out, then, ignoring her snarl, hooks his fingers under his shirt and pulls it up over his head. After another moment of consideration, he gets rid of his pants too.
“Ooh, good idea, take mine off,” Stiles demands quickly, and even though Laura is still growling out threats, Derek laughs and reaches around her so he can drag Stiles’ shirt over his head as well, then ducking down so he can help him shimmy out of his jeans.
Now that he’s not holding her down, Laura is doing her best to fuck Stiles straight into the couch, a frantic edge to her movements that has Derek hastily grabbing for her again, afraid that she’ll go too hard, too fast, and Stiles will come before Derek can even get inside of her with him.
“You fucking asshole,” she snarls, her breasts heaving, white tanktop nearly transparent with sweat. “I am your alpha, listen to me when I—”
She breaks off with a ragged gasp when he starts pushing in, and all three of them go still as Derek works himself inside of her. It’s almost too tight, Stiles’ cock a hard, hot line against his, Laura all tight, wet heat around them. Derek’s toes curl in the carpet and he bites his lip to hold back a whimper, blinking his eyes open again only when he’s in as far as he can go.
They both stay there, panting, and adjusting to the feeling that’s teetering on the edge of too much, too soon, until Stiles gives a whimpery moan and hooks his chin over Laura’s shoulder so he can bite at Derek’s lips.
He falls into the kiss easily and somehow, kissing Stiles changes to kissing Laura.
It should feel new and strange and gross, but he has been dead — Derek has been bones before — and actually has his dick inside her right now, so kissing his sister is not the strangest thing he’s ever done.
They manage a decent rhythm together, Derek smug when Laura realizes that with this position, she doesn’t have enough leverage to actually be in control — that Derek has to do most of the work for all of them.
It’s good though, so very good — Stiles mouthing sloppily at his neck as Derek exchanges biting kisses with Laura, moving inside her in sharp jabs and slow slides. He teases and taunts, pinching her nipples between his thumbs until Stiles’ hands join his, sliding down her belly to tease her clit, until she’s a gasping, jerking mess between them.
They mean for her to come first, so she does, explosively, letting out a wail that rivals some of Stiles’ as she jerks between them.
Derek goes slow as she rides out the aftershocks, melting back into Stiles’ chest with a happy, almost drugged smile. She nuzzles them both, happy and affectionate, and after another moment, she slaps Derek’s ass, which he takes as permission to stop holding back for her sake and pick the pace back up.
He’s less careful, now that she’s come, rutting into her hard and fast. Stiles whimpers, claws sliding out and drawing careful, jagged lines down Derek’s back. He’s floating on a haze of pleasure, so close, kissing Stiles over Laura’s shoulder in between trailing kisses up her neck, so it’s pure chance that he looks down at her as he’s straddling the edge.
She’s looking up at him from beneath heavy, dark lashes, just a sliver of alpha red visible, and there’s a sloppy, warm smile around the edges of her lips as she looks at him and tells them both with just the right amount of command in her voice, “Come for me.”
They come for her — hard and dizzying, emptying inside of her and whimpering through the aftershocks, trembling as she gets her hands on them, calming with a touch.
“Dude,” Stiles pants, shuddering when Derek pulls out. “Please tell me we can do that, like, all the time, jesus.”
Laura snorts, nose pressed into Derek’s shoulder. She makes grabby motions when he pulls away, going so far as to outright whine when he shakily makes his way out of the room and down the hall. When he reaches the linen cupboard he can hear Stiles going, “Woah, wait, where the hell does he think he’s going? Derek, you better not be jumping out the window!”
He grabs a towel, one of the ones closer to the back that they never really use. It’s got holes in it and he’s pretty sure it migrated over with Stiles when he started staying the night more often, but it does the job. He takes a moment to wipe himself down before he heads back to the living room.
When he gets back, Laura and Stiles are slumped over across the couch and cuddling. He’s got his arms looped around her belly, his nose buried in her hair. The image is soft and sweet, and Derek is in no way of ashamed of the way he stops to admire the view before slinging the towel over to them.
“Why the hell would I jump out the window?” he asks, sliding in next to them. The couch is too small for them all to fit horizontally, so he wriggles in where he can until their heads are pillowed comfortably against his thigh. He strokes a gentle finger over the curve of Stiles’ cheekbone, smiling when the digit catches in Laura’s hair.
Stiles gives him a happy, upside-down grin and flaps a hand dismissively, “I don’t know, you’re weird about shit sometimes.”
Laura rolls her eyes. “He wouldn’t be Derek if he didn’t get weird about shit. It’s all part and parcel of the experience. Get used to it, Stilinski.”
Stiles pouts at her, but shrugs, grabbing blindly for the towel and swiping it across his junk. Then, so gently that it could be classified as reverent, starts wiping Laura down. She swipes halfheartedly at him, but doesn’t protest the treatment.
“We should, you know,” she says after a moment of quiet. “Do this more often.”
“Yeah,” Stiles puts in, scooting closer to Derek. With a fair bit of maneuvering, he gets Laura spread out across both their laps and cuddles up against Derek’s side, flopping his head onto the available shoulder. “Sharing is caring, bro.”
Derek raises an incredulous eyebrow. “Pretty sure we’ve gotten damn good at sharing.”
Stiles wrinkles his nose and blows a raspberry. “Yeah, but that’s just sharing me. Trust me, it’ll be way easier to not have to worry about one of you feeling left out because of who’s bedroom I decided to sleep in. This way, we can have awesome sex and awesome sleepovers.”
Derek exchanges a look with his sister and nudges her gently, wiggling his eyebrows in a manner that hopefully comes off as him asking what her opinion on the matter is. She burrows her way further into his lap, nose dragging against his hip. After some consideration, she nips it.
“Don’t know why you’re asking me,” she tells him. “You guys are the ones with the weird relationship issues.”
She laughs at them. “Pretty sure you are. How long have you guys been having sex now? Almost two years? And how many other partners have you had?” She examines a nail, picking some dirt out from beneath it, then clarifies. “—Besides me, of course.”
When they’re both silent, she gives them a smug, triumphant look. “And you still say you aren’t dating. Ergo — relationship issues.”
Stiles looks like he’s going to protest again, so Derek decides to be the bigger man for once. “Okay, so we might have possibly been dating a little. Without the actual dates.”
“So what? Would the three of us be dating then?” Stiles asks, getting that gleam in his eye that means he’s going to be handing them spreadsheets and bar graphs on the subject in the morning.
Derek shrugs. “If you want.”
Stiles leers at him. “Oh, baby, I want.”
“The both of you are idiots,” Laura remarks fondly, leaning up so she can kiss Derek on the nose first, then turns and does the same to Stiles. “We’ll do what feels natural and go from there. It’s that simple. Instinct.”
Derek smiles at her, threading a hand through her hair and bending down so he can press a sloppy, happy kiss to her brow.
“Well,” Stiles says after a handful of minutes. “Right now my instinct is saying to get some grub. I think the diner is still open at—” he peers at the clock. “—half past three in the morning. What say you, my equally furry brethren? Is it a date?”
It is a date — a date spent teasing each other under the disapproving eyes of the lone waitress and, even worse, flinging eggs back and forth. When they get back to the house later, they all have eggs and bits of sausage in their hair, but end up taking turns picking it out when they fall straight into Laura’s bed.
Their next one goes better, but that first date will always be Derek’s favorite.