Would you say there are differences to the sibling's personality to their AU counterparts? Or are they pretty much the same in that regard?
hmmmm. they might *feel* different, but IMO they're pretty much the same in the sense that they have the "same" bg story, morals, preferences (ghosts, wants, needs) but adapted to a vampire colony! xD
that apparent difference comes, i think, from the fact that the siblings are all a lot older in RotBC (a few centuries, give or take XD) and already managed to heal from the pain their father caused them (that part of the story didn't change), so they feel much more comfortable being themselves and exercising their power! ^^ the setting is also a bit different (i imagine a vampire court to be a lot more immediate in its dangers), so their behavior has to somewhat mirror that... but when writing, i make sure to always think "how would Mel/Mand/Matt act if...? and what would it take for them to...?"
that's why i like AUs so much! *-* ♥♥♥ it's such a fun character development exercise, plus it lets me have glimpses in the past/future/what-could've-beens that i wouldn't have otherwise! ♥