Rat's parents are like Rat. He once stated that they were "like a derailed train, but the crashes were great."
Rat's Father (deceased)
Rat had a father who was unfortunately killed by a circus clown. He appears in heaven along with Rat's grandma and grandpa.
Rat has a mother, though she has not appeared in person, Rat had a conversation with her on the phone.
Rat's Cousin (Deceased)
Rat had a cousin who died and Pig misunderstood the term "Going to a wake."
Rat's Grandma (deceased)
Rat had a deceased grandma who he met in heaven. She apparently does not like Rat as she didn't care that he was going to hell.
Rat's Grandpa (deceased)
Rat has a deceased grandpa who first appeared in a strip with Rat's father and grandmother.
Rat doesn't seem to like any relatives as he said the only thing that's worse than not spending thanksgiving with his family, is spending vacation with his family. One year he brought a massage girl with him, to relive the stress. His family treated them poorly, so to make it up to her, Rat invited her to play Trivial pursuit. However, Rat's family appeared to act much like him, cursing, accusing/defending in a crazy manner, and threatining to throw the card box.