As far as I know, you've always been able to have two characters per island, with the exception of Dwilight. Those characters could be either any combination of noble or advy. There was no special exemption for the invasion. It is only recently that the one-character restriction on Dwilight was altered to allow a second character, provided that second was an advy.
Three active, unpaused characters on Dwilight has got to be a bug.
