Pure-blood is the term applied to wizards and witches who have no Muggle blood, Muggle-borns, or half-bloods at all in their family tree. They are the rarest of the three blood statuses, with J.K. Rowling saying 10% of the Wizarding community is made up of pure-bloods. Although technically pure-bloods have no Muggle ancestors, the small wizarding population means that "true" pure-bloods are rare, with some just ignoring or disowning the few Muggles in their family. Identified pure-blood families include the Blacks, Crouches, Fudges, Gaunts (though that line died out before the beginning of "Philosopher's Stone"), Lestranges, Longbottoms, Malfoys, and Weasleys (but the most recent generation has had half-blood members). To maintain their blood purity, some supremacist families have been known to inbreed into their own families by marrying their cousins, resulting sometimes in mental instability and violent natures. The Gaunt family displayed both tendencies by the time of the sixth book.