Eric Cartman
Cartman lives with his mother. He previously had a pet pig and cat, but they both stopped appearing in episodes. In the original pilot episode, Cartman and his mother are seen eating dinner with a man and little girl, presumably his father and younger sister. Whilst episodes have been dedicated about the identity of Eric's father, nothing has ever been said of the mysterious sister. It is eventually revealed that his father is that of Mr. Tennerman, son of Scott Tennerman, Eric's one-time rival. What makes this worse is that, in one episode, he grinds Scotts' parents into chilli and feeds it to him. With this information, that means that in reality, Eric grinded up his own Father.