I'll fix it later. Damn phone capitalizing things.......

You concept of blood magic is acceptable but I wouldn't call it Dark or even give it a Dark Affinity. The inherent traits of the vampires and their magic could be considered a tribal magic since it would be unique to just them. And since they aren't actually vampires I don't really have much else to say on the matter. What you have so far is good! I like the idea of having some traits of some maybe unwise decisions in their family's history.