Where are you finding all this BSC slash? I've read one story about the Pike triplets (excellent, but still just the one), and then I'm a member of bsclove, which does not feature fic as often as I'd like, but which does have a great deal of all sorts of babysitter pairings. And Stacey/Charlotte, which, as hermionesviolin implies, is practically canon. But then, it's a girls-only kind of place.