Sirius is messy and stupid and raw and stupid some more, and Remus Lupin can't stop fucking him. Oh, god, he'd love to, sometimes, just after, when Sirius says something stupid about how he's not gay, you know, he's not some fucking poofter, it's just sex. The fact that he's saying this right after he's come in Remus's ass, that he's saying this as he pulls Remus's cock into his mouth, that he's saying this into a pillow as Remus pounds into him — of course, Sirius is so fuckingstupid he never seems to understand how stupid it is to say the stupid, stupid things he's saying.
Oh, god, the rows they've had, and Remus throwing shit and casting hexes and kicking Sirius out, and then crying, hot tears and utter broken rage because Sirius is never going to see him, never going to get over the gay thing. His family'd fucked him up, of course, all that shit about the Black family name and being an heir to the blood and all that, and Sirius still thought he'd meet some foxy witch at Hogwarts and fuck her for a while and get married, pop out a kid, and that Remus would just, what, fade away?
And Remus, he's no idiot, he knows Sirius wil never be able to think of him that way, will never see him for anything but a friendly fuck and someone to bum a fag off of, and Remus knows this, he knows it. But sometimes, when they're fucking or grinding or kissing, hurried and wet in an alley or a corridor or a dark room, sometimes Sirius says other things. Whispers into his neck or his mouth or around the cock in his throat, hisses and gasps and moans things. And Remus shatters and smiles and falls a little more in love with this wild broken boy, because oh god they'd be so good together if only Sirius could see it.
For some reason, though, it all stops after James and Lily get married. Remus doesn't think Sirius was in love with James, exactly, but he'd always seen something in Sirius's eyes when the Potters were around. And he knew it wasn't Lily that Sirius was looking at; for all Sirius's protestations, Remus knew that unlike himself, Sirius was utterly uninterested in sex of the hetero variety. But they don't really talk, after the wedding. Then, when the baby came, they kept away from each other. Sirius somehow managed to schedule his visits around the full moon, when Remus wouldn't be able to.
Then, a couple years later, they met accidentally at a bar in Godric's Hollow. They danced and drank and it was like old times, and Sirius hissed in his ear and Remus felt a thrill of the old magic there, he thought maybe, maybe now that Sirius knew he'd never have James the way he'd always wanted…
But then Hagrid appeared, tears in his beard, and Sirius had given him the motorcycle, and they'd gone back to Remus's and fucked, raw and angry and keening, trying to push away the rage and pain and loss, and Remus had screamed, over and over, into the mattress as Sirius thrust into him blindly and silently and furious. When he'd come, Sirius had pulled out and dressed, fled, hadn't even looked at Remus. The next time Remus Lupin saw Sirius Black, it was in a photograph on the cover of the Daily Prophet, and Remus cried for hours because it was obviously, patently not true but no one would ever believe him, and the last thing Sirius had said to him was all that stupid shit about not being a fucking faggot, oh god.