Wouldn't be necrophilia if two undead creatures have sex, its a living and dead person that is.
@Angel: The body parts thing isn't necrophilia, munging involves a dead woman, but is not considered necrophilia.
The bleeding/blood flow thing depends on what you want to believe, many different variations of vampires done by a ton of different people and mediums. In Vampire The Masquerade they don't bleed and among my gaming group we always said you needed to spend a blood point to "make it work" and an additional point for the climax part which we sometimes used to blood bond people.
I don't think the blood kiss is all there is to it either. In most things concerning vampires they exist because of nature, the devil or as a curse. Since vampires in warhammer came about because of magic, I would think at least some incantation as well as the transference of blood would be needed to create a new vampire from an existing one. Vampire Wars has me thinking differently though, Vlad sires Isabella and Jerek pretty much by the j random standard I drain you then I feed you some of my blood and they wake up hours later as a vampire.
I just gotta say, The Necro Files, look it up, bad B horror movie with an undead rapist so the necrophilia is a bit backwards.