Gerard Mystery is the father of Martin Mystery and step-father of Diana Lombard when his son and stepdaughter were very young. He is a very strict man, but he is also caring towards Martin and Diana. He isn't into the paranormal and supernatural since he showed up in the 3rd season of Martin Mystery.
Gerald bears some resemblance to his son Martin.
- He taught his son how to twist the lynx' ears when they tried to bite Martin.
- He eventually learns about Martin and Diana being Center agents alongside with finding about Java, Billy and M.O.M in the episode "Wrath of the Torrington Worm".