I'm not taking a position on this yet, but there is a cultish belief system out there about bloodlines, the "mark" of Cain, Annunaki, etc.
The whole bloodline thing might have been the result of Haemolytic disease–is the allergic reaction that occurs when an Rh negative mother is carrying a Rh positive child. Good breeding, inbreeding, etc…
http://seemytruth.blogspot.com/2010/08/rhesus-negative-blood-and-annunaki.html