Ancestors are the original vampires who evolved from humans over ten thousand years ago during a climate change, which resulted in the post-apocalyptic timeline that Vampire Knight currently takes place in. Ancestors and their full-blooded offspring were later to be known as Pureblood vampires. Ancestors, also known amongst themselves as founders, due to being the very first vampires in existence.

The mixed blood of the Pureblood vampires, and that of lower class vampires or humans, is the cause of the Aristocrats vampires ranked below the Purebloods.