Ted: Alexander and Melanie wouldn't know him, sadly. Remus might know him, depending on whether or not Remus has been with Sirius when he's visited? Perhaps, perhaps. We'd have to talk to both Joan and Lily about that, but if they agree that it was possible, then I see Remus having no trouble with Ted at all! I think he'd really like him, actually.
Lily: Remus would adore Lily! I imagine they did prefect rounds all of the time from fifth year onwards, which might have brought them closer. He also has the advantage of not being a bullying toerag like his friends. So! Close friends for sure. Melanie would also like Lily, and would partake in the name calling of the Marauders with her! Mel has a bit of history with Sirius, so boy bashing can totally be on the cards! Alexander dislikes her immensely and probably hasn't hidden that in the past. They're both prefects, which could cause lulzy moments in future!
Antonin: Oh, you. Melanie and Remus both have no idea who he is. Alexander might have seen him once or twice at Death Eater dinner parties and the like? Other than that, I can't see anything else.