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.
Gerard is very similar to Diana they are both serious, smart, Brave, rational, Obsessive, They both get annoyed by Martin's Childish behavior.
Gerald bears some resemblance to his son Martin. He also has a beard.
Gerard loves his son and hope that he would become a good person. Gerard is annoyed by Martin's childish behavior, by the fact that he doesn't study or work hard in school or by his pranking joke on other people.
Gerard loves Diana and they have a good father - daughter relationship. He appreciates her especially for being responsible, smart, doing hard study and work in school and for not pull pranks on people like Martin does.
- 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 out about Java, Billy and M.O.M in the episode "Wrath of the Torrington Worm".