"Unk" is Uncle Rusty Bryant, Aunt Sherry's husband. (Aunt Sherry is Sonya's sister, MeMaw & Pop's daughter). Unk is also the father of JoJo & Ray-Ray.
Haylee used to help Unk feed his turtle. He fed the turtle worms, and this caused a bit of worry for Haylee, who loved worms. Unk had to tell her he only fed "bad worms" to the turtle. So every time Haylee would help him, she always asked "Unk, is this a bad worm or a good worm?" before she'd feed it to the turtle.