Thor doubts him sometime.
He doesn’t say anything out loud, but it’s there, flitting around the corners of his gaze. It seeps into the silence between them sometimes.
Odin had thought that it was better to separate them. They both think it’s because of the potential of what they could be — but in different ways. Thor thinks they were intended for such greatness that Odin feared them. Loki thinks that they have achieved that greatness by reveling in what they have done. Their father sought to separate them, whispering callously that they weren’t brothers anyway. He meant to send Thor to one realm, and Loki to another, stripped of what they are, stripped down to fragile flesh and bones without a hope of finding each other again.
It’s Loki who spurred Thor to action, the two of them able to easily overtake Odin. Odin doesn’t stand the scarcest of a chance when it’s the two of them together, Loki’s magic weaving up and along Mjolnir. Thor does not panic then, because the lie that it was the Frost Giants comes tripping easily off their tongues.
Thor does not doubt when he first goes into battle with the Frost Giants, or when he comes home covered in blood, the very essence of it steeped in his pores. He does not doubt when he takes Loki up against the wall of their bedroom, or when they are declared the Kings of Asgard — meant to rule together. He does not doubt — not at first.
But the time grates on Thor’s conscience, and Loki should have known that this would happen. He can’t look their mother in the eye, and he seems almost listless when he’s not in battle. The war is not the game he thought it was.
He doesn’t see Thor for days after his brother first sees him as a Frost Giant, his skin glinting cerulean blue, lines pressed along his flesh. He can hear the thought that ricochets around Thor’s mind — they were never brothers.
And Loki thinks it’s time to build themselves into something beside what Odin intended them to be; he needs some way to reclaim his brother.
When Thor returns to his bed, Loki does not wait for him to act. He wraps one hand around the back of his brother’s neck, fingers playing through his golden strands of hair as he kisses with purpose. His teeth play along Thor’s lower lip, sinking into tender flesh until he splits the skin. It’s only then that he draws back slightly, his tongue probing, lapping up bead after bead of blood.
Thor’s eyes are wide, the black of his pupil almost swallowing the blue. He lets out a low noise in the back of his throat, and that’s all that it takes before he’s leaning forward, covering Loki’s lanky body with his own. He stretches them across their bed, covered in the furs that Thor has brought back from hunts over the years.
He devours Loki’s mouth and all Loki can do is arch up into his brother, pressing his bloodied tongue up into Thor, letting it draw his claim on Thor across the roof of his mouth.
Thor seeks to pin him down, his large hands seeking out Loki’s wrists. But Loki keeps himself moving, twining his arms back around Thor’s neck. He drags his brother closer, rolls his hips up against Thor’s. He can feel Thor’s cock straining against him, riding against the jut of his hip. He lets his magic skitter across their bodies, leaving them bare. He can hear Thor growl.
Thor’s hands run possessively down his sides, reaching for his hips. His fingers linger there, pressing hard enough to leave bruises, marks of ownership.
And at the same time, Loki pulls one of his hands away from Thor. It’s a simple twist of his wrist, his fingers plucking at the open air, and he has one of his knives in his hand. Mjolnir may suit Thor, but Loki will never understand the appeal of a weapon so blunt. He prefers the precision and the grace of the knives that fit silver sleek against the palm of his hand.
He kisses Thor again, all teeth, against the sides of his mouth. He lowers the knife, fits it right beneath Thor’s shoulder blade and drags it down, letting it slide along his back, curling toward his hip at the bottom. Something giddy rises inside him when he feels his brother’s skin give way beneath the blade, the rush of blood that rises to the surface.
Thor rears back the moment he feels the knife, his eyes flashing dangerous.
“Loki,” Thor says, his voice low, echoing with the promise of thunder.
Loki shushes him with quiet clicks of his tongue, pressing his now-bloodied fingers against his brother’s mouth. He maneuvers them on the bed, flipping Thor onto his back, straddling his waist. Anger still flashes underneath his brother’s skin, lightning sharp; Loki lowers the knife again before Thor can do anything to stop him. Thor’s brute strength will always outpace his, but Loki is far quicker.
He draws an arching line along Thor’s shoulder, pauses for an instant, and curls a line across the top of his bicep. His gaze flicks up to his brother, and in that moment, he sees Thor’s understanding. The doubt is still there though. It presses to the surface; Loki does not wish to see it. He moves on with his work. His fingers bite into the blade of the knife, breaking through his own skin as he continues to trace lines open on Thor’s arm. His blood drips down the silver, mingling on brother’s golden skin.
He begins to grind his hips forward, back and forth. Thor moans, and Loki watches the way his pulse quickens in his neck, his eyes fluttering.
He carves his brother open, mirroring the marks that adorn his own skin. He can feel them raise dangerously to the surface of his own, seeking to make them a mirror image of each other. Thor’s blood is hot upon his hands. The first arm goes quickly, and by the time he’s tracing the line along the runes of Thor’s other arm, Thor is trying to reach for his hips again. His body is a torrent of motion, his face feverish.
“Brother,” he moans, his voice low.
“Brother,” Loki whispers in return. His hands are sleek with Thor’s blood, and it’s almost difficult to still hold the knife. He leans in, fitting his mouth over Thor’s collarbone. He begins to suck roughly; Thor’s blood is burning and salty, coating his throat and slicking the back of his throat. He groans, unable to hold the sound that gathers in his ribcage. It reverberates through the both of them. Loki pushes his hips forward, their cocks aligning. Thor shudders beneath him.
For a brief instant, Loki wishes that Odin could see his favored golden son like this, splayed beneath the devious second son, Jotun markings upon his body, his precious Aesir blood on the mouth of a Jotun.
Thor quickly chases those thoughts away. He grabs Loki by the back of the neck, his touch rough and commanding. Loki has erased the doubt from him. Thor thrusts his hips up as if he’s fucking Loki already, and Loki pulls away enough to drag the knife back over Thor’s chest. It’s difficult to work, Thor’s body moving so erratically, but he continues anyway. His blade skitters over the sensitive skin over Thor’s ribs, curls down his navel. The knife is balanced precariously in between them; Loki feels as if he were to breathe too sharply, to move too quickly, he would be cut as well.
It’s more difficult to work this way, the lines less precise, but neither of them can be damned to care at the moment. When Loki finishes, he tosses the knife to the side, letting it bloody the sheets a few feet away from them. He runs his hands up along Thor’s body, marveling at his work. He feels drunk with it, Thor’s body slick with red and heat.
“I’m taking you,” Thor growls. It’s all the warning Loki gets before Thor adjusts his body and begins to press up into him, the pace agonizing. Loki stifles a moan, his head tilted back. His hair sticks to his neck, and he’s quietly overwhelmed. He grips Thor all the tighter.
Loki tries to rock his hips, tries to take some control of the situation back, but he’s set Thor loose, and Thor merely holds him down. He hammers into him, back arching off the bed, seemingly unaware of how he’s bleeding out onto their sheets. Loki traces the lines the best that he can, weaving faint magic along Thor’s skin — enough that the marks will heal well, but remain. Faint scars that mark them both.
His orgasm takes him almost by surprise. He tightens with a gasp, spending himself over Thor’s stomach. He goes lightheaded for just a moment, the room spinning about him. It’s too heat, and the smell of salt is sharp. Loki presses his knees more tightly against Thor’s sides as Thor continues to thrust, but his brother is right there with him, moving once, twice more, becoming as well.
He yells as he comes, his head tossed back against the bed. The ends of his golden hair is plastered against his skin, colored red.
Loki falls forward as soon as Thor releases his hips, and he licks up the side of Thor’s throat, his tongue laving praise against Thor’s pulse.
Thor breathes unevenly for several moments before grasping him by the neck once again. He pulls him up, and kisses him roughly once more, cleaning the blood from Loki’s lips.
“My king,” Loki murmurs against Thor’s mouth, his fingers tracing the wounds along Thor’s shoulder, as if he would imprint the word there.
“My brother,” Thor returns in a growl. Loki smiles.