I'm BB and my boys are the Professor and Charles. Both are humans (a sorcerer illusionist, and a psychic cowboy), and have been around Zion for a little bit. Professor Blackstone for 11 years (joined up in 1908), and Charles for 2.
James likely knows Sean, or at least of him, since the sorcerer is a fan of learning all he can about magic. Even from a different sort of caster. He runs a tent show of sorts, and makes/sells magic trinkets, potions and that sort of thing too.
Charles doesn't really put much stock in that magic mojo stuff (he doesn't even know he is a psychic either), so he wouldn't likely swing by Mayfair's tent. Still if Sean is one for poker or drinking the gentleman/cowboy is always hosting a card game. Just beware...he is a bit unnaturally lucky. Lol.