Because of the nature of the musebox fantasy thingy, I would accept all of these, with conditions for some of them.
Original fandom characters - I'm okay with "no close relations" however, as I'm sure that would dampen some people's fun, maybe we can work around this with some rules, like express permission from current close cast to be their wife/husband/father/mother/child what have you. I wouldn't want somebody to come in and say "i'm your wife" when the other person didn't want that.

Personally I'd extend this to not allowing those types of characters without a close cast character present, but again I don't want to be too restrictive either. Tough call.