How do you know if you were a vampire in past life?

Fortunately vampires do not figure in the re-incarceration scheme. In order to have a past life you have a past life in which you were alive. Vampires are not alive, they are the undead. So if at any time you had a past life in which the body from that life became a vampire it doesn't effect your linage, it is skipped over. In fact, a person could be re-incarated while his/her body from a past life is still running around as a vampire.