Somewhere, in the heady, cloudy thick of it all, tangled up in the drive of Regulus's hips against his own and the flush in Regulus's cheeks and the way Regulus's eyes had gone just a bit hazy, some scrap of James's mind couldn't quite buy it. Well. It could. But not quite.
Regulus had to be.... joking. Except, it wasn't funny. But he couldn't be serious. Fuck. Sirius. Sirius would kill him. Then again, Sirius would have killed for the last few hundred times James had fucked his little brother, too. And really, James would be hard pressed not to let him.
But Regulus Black was not really laying down rules for how this... thing was going to work. Right? He wasn't actually, out loud, agreeing to this nonsense, without James having to prompt and lure and needle. Because that would've just been way too much. It would have been too much to pass up. So that couldn't be what was actually happening.
But, on the off chance that it was-- No. It wasn't. And to prove that it wasn't, James played right along. Surely, Regulus would balk. Eventually. One of his hands dragged Regulus's collar away from his neck, exposing a bit of his shoulder for James's mouth to find. "No marks," he suggested, an instant before biting hard enough to leave little red crescents against Regulus's flesh, "on my skin."