You transferred all characters at once? This is a valid way to do it but I would always be worried that one or more characters might arrive before the kinship leader character. In that case they will arrive but their kinship doesn't exist yet.
So I would always transfer kinship leader first then house owner then shared account stuff then rest of the characters and always wait until one transfer is done before doing the next. I think that this is the safest way to do the transfers.
Yes I did the whole shebang in one go.
What you suggest seems quite possible and very likely. The expelled character was actually listed before my main (kinship leader) character in the character listings. So it is totally plausible that she arrived on the server before the main who was kinship leader. I would have (to use that awful word) ASSUMED that Turbine would check for kinship leader and move the kinship fact first, but not thinking of that would not surprise me or not providing a warning to the player whose character is the kinship leader. Well, I might not have paid too much attention to a warning.
At least they should provide the capacity, like a bound token, for a character listed as expelled from a kinship as a result of the transfer but that would be of use to sparsely populated kinships since a well-populated kinship would be able to work around that fast.