We know Abnur himself has had multiple wives, and at least sixteen daughters. He has several siblings (Euraxia Tharn, and Veraxia Tharn come to mind) who have likely had many children of their own, and then their children probably had children as well.
Whether or not they're all evil is difficult to say, but since their family is so closely tied to the conflict in Cyrodiil, I imagine that many of them would have followed Javad, Septima, and Clivia's example and thrown in their lot with the worm cult. I get the feeling that most of them are morally bankrupt anyway.