I'm posting this now because I personally get annoyed when I find out later that I've been playing with side 'verses of characters without knowing it. So I'm making this now before things get complicated.
If you're not among the people who are directly involved in one of David's side 'verses (the ship-related ones, not the obviously different ones which are always marked) or whose canon conflicts with his main 'verse, David's default is one where he and Aubrey are starting a relationship. There's a mess with Jac that David's still sorting out, but he's picked Aubrey. This applies to all casual meetings as well as David's other friends (not least because telling Mel he's dating his lookalike is going to go over horribly and I want to see it).
For the big splits, which are always marked,
Changeling 'verse is primarily played in memes with Aubrey only, but is open to other play.
Hunter 'verse is likewise meme-only at this point, and is open to anyone.