Uncle Quentin and Aunt Fanny George's parents and uncle and aunt to Julian, Dick and Anne.
Joanna the Kirrin's faithful cook! She gets involved in many adventures!
Alf The fisherboy who looked after Timmy before George's parents allowed him in the house. First seen in Five On A Treasure Island
Jennifer Mary Armstrong the daughter of millionaire Harry Armstrong who the Five rescue from kidnappers in Five Run Away Together
"Sooty" Lenoir and his sister Marybelle. The children of one of Uncle Quentin's colleagues. They share an exciting adventure in Five Go To Smuggler's Top
Nobby a circus boy (with his chimpanzee "Pongo") befriends the Five in Five Go Off In A Caravan
Martin Curton helps the Five in Five On Kirrin Island Again. His father plotted against Uncle Quentin.
Mr Luffy a teacher from Julian and Dick's school who "looks after" the Five in Five Go Off To Camp.
Jock Andrews a farm owners step-son, also seen in Five Go Off To Camp. He helps the Five solve the mystery.