Over the course of Scooby-Doo’s various spin-offs, various relatives of Scooby were introduced:
Scrappy-Doo: Scooby’s young nephew (and son of Scooby’s sister Ruby-Doo), Scrappy is the bravest of Scooby’s relatives. Scrappy became a recurring character in the Scooby-Doo series beginning in 1979, and was noted for being quite headstrong and always wanting to face off in a fight with the various villains (unlike his uncle). He has one or two catch phrases, the one he uses the most is “Puppy Power!” Scooby and Shaggy were present at Scrappy’s birth.
Yabba-Doo: According to Scrappy and Yabba-Doo Yabba is Scooby’s brother, a white dog owned by Deputy Dusty in the American Southwest. Unlike Scooby, Yabba is brave. Unlike Scooby’s and Scrappy’s, his typical custom catchphrase at the end is “Yippity-Yabbity-Doooo!!!” (and not “Yabba-Dabba-Doo!”, presumably due to another Hanna-Barbera character’s usage of that phrase).
Scooby-Dum: Scooby’s cousin (according to Shaggy in “Headless Horseman of Halloween), a blue-grey dog. A Mortimer Snerd-esque dog who longed to be a detective. Was rather dimwitted (he would keep looking for clues even after the mystery was solved). His catch-phrase was also different then Scooby’s and Scrappy’s. Instead of “Scooby-Dooby-Dum” his typical custom catch-phrase is “Dum dum Dum DUM!”, an intoning the opening four notes of Beethoven’s Fifth Symphony, which he would do after someone said the word “clue”.
Scooby-Dee: Scooby’s distant cousin, a white dog. Spoke with a Southern accent, and was an actress.
Dooby-Doo: Scooby’s cousin, a singer. He is one of Scooby’s few relatives to have hair on his head. Only appeared in “The ‘Dooby Dooby Doo’ Ado”.
Momsy and Dada Doo: Scooby’s parents. His mother is the only one who calls himby his full name, “Scoobert”.
Whoopsy-Doo: Scooby’s cousin, a clown. Owned by Shaggy (Norville)’s uncle, Gaggy Rogers.
Ruby-Doo: Scooby’s sister, and mother of Scrappy-Doo.
Skippy-Doo: Scooby’s brother. Highly intelligent; he wears glasses.
Howdy-Doo: Scooby’s brother. Enjoyed reading supermarket tabloid newspapers. He appears to become a redhead.
Horton-Doo: Scooby’s uncle. Interested in monsters and science.
Dixie-Doo: Scooby’s cousin and the pet of Betty Lou, Shaggy’s Southern cousin.
Grandad Scooby: Scooby’s grandfather.
Great-Grandpa Scooby: Scooby’s great-grandfather.
Yankee-Doodle-Doo: Scooby’s ancestor. He was owned by McBaggy Rogers. He also appears to be a pilgrim. Little is known about him.
Spooky-Doo: Scooby’s uncle. He was the former owner of Doo Manor.