Cartman is the fat one, the rude one, the racist one, the...well you get the idea. His father is a hermaphrodite named Liane, and his mother is unknown. His father, Liane, constantly spoils him with whatever he wants. She also leads a life of sex, drugs, and posing for Crack Whore Magazine and German sex videos. Cartman has an ongoing feud with Kyle. He often tries to kill Kyle but never succeeds.
Kenny the Poor one. He has a relatively unseen brother named Kevin. His father, Stuart, is an alcoholic who can't hold a job, and his mother often gets angry at his father for being a "nuggity deer terd." Kenny has an uncanny knowledge of anything to do with sex. He often informs the other boys about something when they don't know what it is. He is almost always wearing a parka with a hood that covers his face and muffles his voice. He died almost every episode until the end of season 5, when he died for real. He did not come back until the very end of season 6.
Stan is the "cute" one. He has a sister named Shelly who is bigger than him and bullies him. His parents, Sharon and Randy, often treat him with condescension, and he hates them for it. He also has a grandfather who wants to die. He often brings some sense to a difficult situation. He is always trying to woo Wendy Testaburger.
Kyle is the Smart, Jewish one. He has an adopted Canadian brother named Ike. His parents, Shiela and Gerald, are very strict, especially his mother. He is often bothered by his conscience when the boys do something wrong.