Scooby-Doo and Guess Who? is the first series to not technically feature any relatives of the gang. It's explained in "What a Night, for a Dark Knight!" that Alfred Pennyworth was actually Daphne's family's butler that they affectionately referred to as an uncle, but he is not actually a member of their family.
Thanks to my friend Deandre (aka Scoobyfan4ever) for coming up with this week's fun fact!
~ WildwindVampire ~