"Which Remus?" It struck Peter, as he asked it, what a ridiculous question that was, on the face of it. But this was the sort of place where you had to ask questions like that. Not for everyone-- not for him, for example, there was only one of him here-- but for Remus, there were multiples of them. And he had not been keeping track of which one in particular Sirius had been hanging out with. The only thing he knew was that it wasn't their own Remus, because their own Remus wasn't here.
He did understand how that worked, though. How you could just hang out with someone here, in a way that you didn't normally, and find a friendship-- or in this case, a more-than-friendship-- without even really trying to. He never would have spent this much time hanging out with Hestia back home, and there wasn't even a chance to spend time with other people here if they weren't from his own world.
The worlds apart thing made it more difficult, he supposed. It meant that the relationship could only exist here, in a different way from how his and Hestia's could only exist here. They'd still be friends and in-laws of a sort back home. A person from a different world wouldn't even really exist for them at home-- because whatever this Remus was like, he wasn't the one they'd grown up with. He didn't know what else to ask, except, "That's a good thing, though, right?"