Uncle Scooby

Uncle Scooby was Kade and Nicole's uncle. It's unknown which of their parents he is a sibling of. Nicole noted he had a speech impediment, and liked telling them ghost stories. He lived in a mansion, which had a library of books on mysticism. He was revealed to have died early in the comic, and left his niece and nephew his mansion. They renamed the mansion from "Doo Family Estate" to "Savestate Manor".

Trivia

 * Uncle Scooby is obviously a reference to the main character of American cartoon franchise Scooby-Doo. His addition to the comic came shortly after the real-life death of DJ and voice actor Casey Kasem, who played the voice of Scooby-Doo's owner and best friend, Shaggy.
 * Given the connection, it's likely (though not 100% certain) that Uncle Scooby was a Great Dane.