my only problem with this legacy system is that once you put a character between two others, all other choices except child or adopted child are locked. that bugs the crap out of me.... grr. no clue why they would do that.
anyway... interspecies relations are all over the place. also, it's a huge galaxy, there's gonna be some family names repeated somewhere. like with mine, some of my characters aren't related, they're just allies/rivals. but of course they share the same last name. it's just like last names irl.
Jupp, I've come across that bugg as well. Mighty irritating.