Work Text:
They know Loki is an omega long before he even presents, so his first heat isn't supposed to be a surprise; they're expecting it, know it would happen.
Only that it comes more than a year earlier and Loki is not even seventeen yet and he's definitely not prepared for this.
And neither was Thor, who came back from a quick trip to the grocery store only to find his little brother moaning and writhing on his bed, the scent of ripe omega in heat hitting his nostrils, making him almost dizzy with arousal.
Thor just stood there at the doorframe of his room for a long moment, shocked and completely frozen in his tracks, eyes glued to the sight before him, his cock swelling into full hardness in seconds as he kept watching Loki on his hands and knees, fucking himself with three fingers.
He knew he should have left, should have run as far away from Loki as possible, but he was unable to do anything but keep watching, taking in every little detail, like how beautifully his little brother's flawless, pale skin shone with sweat, how his whines got louder every time he pushed his fingers in, how easily his greedy, little hole welcomed the three digits inside.
So, when Loki turned to look at him and moaned Thor and brother and Alpha, begging him and telling him that he needed him, his voice desperate and the words turning into a broken sob at the end, Thor could do nothing but nod and give him what he wanted.
He had imagined and dreamt this exact scenario so many times ever since the first kiss they shared when Loki was thirteen, and even more since he officially presented as an Alpha and Loki came to his room that night to tell him that now Thor could be his Alpha.
So, really, this wasn't a surprise.
Thor didn't hesitate as he got rid of his clothes and climbed into the bed, growling as Loki removed his fingers, arched his back and spread his legs even wider, all but presenting himself to Thor.
It was easy to just slide inside his brother's hole that was already dripping wet, his heat having prepared him for an Alpha's cock, his body eagerly welcoming the intrusion.
It's been almost an hour since then and Thor has already come inside him once, but Loki doesn't seem nearly sated even after several orgasms. But, of course, this was to be expected; Loki is an omega in heat, Thor knows only his knot will truly satisfy him.
A loud whine coming from Loki breaks Thor out of his thoughts and he groans when Loki clenches tight around him, making his hips falter for a moment before he continues fucking into him at the merciless, hard pace he has built up. It seems to be exactly what his little brother needs right now, if his moans of yes and please and just like that are anything to go by.
Thor keeps pounding into him relentlessly, his balls, still full and heavy, slapping against the back of Loki's thighs every time he thrusts in, his grip on his brother's slim waist tightening as he slides inside his delicious, wet heat. Loki's scent has only grown stronger since they started and it makes Thor’s mouth, desperate to taste his delicious slick. And he absolutely would, if he didn't feel like he would actually fucking die if he pulled out of his brother's tight body right now.
Thor's need to fuck and claim and breed and own Loki in every single way is growing stronger and more intense as they keep going, almost overwhelmingly so, and Thor starts to suspect that Loki's heat has trigger his rut. He honestly wouldn't be surprised.
He grunts deep in his throat as he looks down at Loki's ass, right where they're connected and he disappears inside his little brother, loving how they both glisten with Loki's slick; Loki hasn't stopped dripping, it's amazing. Thor's countless dreams and fantasies can't even compare to the real thing.
"You feel so good around me, baby. I've wanted this- you for so long, you have no idea what you do to me," Thor rasps, the words escaping him without much thought, and he continues, encouraged by the wanton moans Loki lets out in reply. "Want you to be mine, Lo. Want to claim you and fill you up, stuff you full with my cum until you're bred and sated and mine. Do you want that, baby? Wanna be mine?" He asks, even though he's quite sure he already knows the answer.
"Yes, yes brother, please. Need your knot, Alpha. Need it so bad- please, please," Loki begs, words coming out needy and slightly slurred, and he rocks his body, trying to get everything Thor has to offer, still insatiable, even with Thor's fat cock splitting him open.
He knows Loki isn't lying when he says he needs his knot, but Thor is not there yet. It won't take long but for now Loki will have to wait. Wanting to at least give his little brother something, he slides two thick fingers inside his hole along with his cock, reveling in the way Loki's breath hitches, a broken whimper following. It's nothing like a knot of course, but it'll do for now; his brother certainly seems to think so. Loki sounds beautifully wrecked and Thor can see tears sliding down his cheeks and onto the pillow, his wet eyes shining prettily.
He's absolutely gorgeous and Thor tells him so, fucking him both with his cock and fingers, Loki's rim stretching widely around them, looking red and used and puffy. Thor can't wait to see it afterwards, when they're done.
"Just a little bit longer, baby. I'll give you what you need, Lo, I promise. I've got you, okay? You're being so good for me," Thor tells him and Loki mumbles something in reply that's not really coherent, his whole body shaking with need; Thor isn't really much better either.
He withdraws his fingers then, so he can lower himself over Loki, pressing his chest to his little brother's back. He doesn't waste any more time before starting to piston his hips forward, ramming his cock into Loki's eager body, delivering one sharp thrust after the other.
He buries his face into the crook of Loki's neck, inhaling his intoxicating scent, kissing and licking and sucking on the sweaty skin of his throat. Loki smells and tastes too good and it all feels right and perfect, like his sweet, mischievous, little brother was made just for him; Thor truly believes that.
He groans helplessly when he feels his knot starting to swell and it's so overwhelming and wonderful and amazing, Thor didn't know anything could feel this good. He keeps fucking Loki for a while, forcing himself to slow down a little, his knot catching at Loki's rim with every slide in and out, still fattening up.
"Almost there, Lo," he says, panting, and Loki only whimpers and nods his head, his hands clenching around the sheets beneath them. It's not long before slipping out of Loki gets almost impossible and he fucks in one last time, burying himself inside his brother as deep as he can, just as his knot locks them together.
Loki sobs in relief and his whole body shudders with his orgasm, his hole quivering around Thor, who follows right after him. He rolls his hips and grinds his knot into Loki as he starts spilling inside him, his cock twitching almost violently, shooting spurt after spurt of cum in his brother, marking him from the inside as well, filling him up.
It takes Thor several moments to stop coming and by the time he has emptied himself in Loki's hole, he's panting and exhausted and absolutely satisfied and content, like he has never been before.
He kisses away the tears that are still streaming down Loki's flushed cheeks and then carefully moves them around so they're both lying on their sides.
They fit together perfectly, like two pieces of a puzzle, and Thor sighs happily as he wraps Loki in his arms and nuzzles the back of his neck.
"Lo? You okay?" He asks, his voice coming out unsurprisingly rough after all the moaning and grunting. Loki hums, sounding tired but happy, and turns his head to press a sweet kiss on the corner of Thor's mouth.
"Always wanted it to be you," he murmurs, the words bringing a smile to Thor's lips. "My Alpha," he says possessively and tugs at the arm Thor has wrapped around him, tightening the hug.
"My sweet, wonderful Omega. I'm so glad I was here for this, Lo," he says, hating the idea of Loki going through this alone. They're lucky Thor decided to visit this weekend. Even though, Thor can’t help but wonder if him being there had anything to do with Loki's heat coming so early. Either way, he's grateful he was able to take care of his little brother.
Not that it's over, yet.
"Now what?" Loki asks and slightly shifts backwards, squirming a little on Thor's knot, making them both moan.
"Now we wait until my knot deflates. And then I'm gonna fuck you again. It's your first heat so it might not last very long, but it's not over, I can still smell it on you," he says, feeling shivers rising over Loki's skin. "I'll take care of you, okay, Lo?"
Loki nods. "Okay," he says softly and relaxes in Thor's embrace, trusting him completely.
They still have a few hours until their parents get home and Thor is determined to make the most of them.