User blog:Roman Never Gets Blocked/Extended Relatives in The 5th Grade Tales of Captain Underpants

George Beard: Uncle Mason (brother of George's father)

Harold Hutchins: Heidi (younger sister of Harold, previously mentioned or seen in books)

Steve Yamaguchi: Uncle Raymond (twin brother of Gooch's father)

Erica Wang: Isaac (younger brother of Erica)

Dressy Killman: Aaron (older brother of Dressy)

Melvin Sneedly: Mabel (Melvin's aunt which is Mackenzie's older sister), John (Melvin's uncle which is Gaylord's older brother), Ciana (older sister of Melvin), Nathan (male cousin of Melvin), Samantha (female cousin of Melvin)

Temporary Sophie: Hannah (older sister of Temporary Sophie)