Terry's father, who was killed during the first episode of the series.
- Amicably Divorced: Though the JLU episode "Epilogue" reveals that Bruce is the boys' biological father, opening up the possibility that suspicions of infidelity on Mary's part may have been a factor, since Terry and Matt's black hair is genetically improbable, given his brown hair and Mary's red hairnote .
- Disappeared Dad: He dies before the third act of the pilot.
- Good Parents: Terry remarks on what an amazing and great father Warren was in "Epilogue".Terry: (to Bruce) My dad was no superhero. He didn't save the world from the near apocalypse of '09. He never went toe-to-toe with Mr. Freeze, but he was a good man just the same. Even after he and mom got divorced, he always tried to do the right thing. My brother and I were always provided for. When mom couldn't quite make the bills, he always helped out. Tried to teach me right from wrong. Would've too if I ever listened to him. And he never laid a hand on me, although Lord knows I was asking for it.
- He Knows Too Much: He gets killed for learning about the mutagenic nerve gas.
- Nice Guy: Warren was often described and shown as a decent person.
- Sacrificial Lion: His death starts Terry's path to becoming Batman.
- We Hardly Knew Ye: As he was only around for part of the first episode and a cameo in the season two finale of Justice League Unlimited.
Appearances: Batman Beyond | Batman Beyond: Return of the Joker | Justice League Unlimited
Terry's mother, who works at Astro-Tech as an astronomer. She approved Terry working for Bruce Wayne, having no clue that it's more than just being a chauffeur to the multi-millionaire.
- Alliterative Name: Both her first and last names start with "M".
- Amicably Divorced: Though the JLU episode "Epilogue" reveals that Bruce is the boys' biological father, opening up the possibility that Warren suspected Mary of infidelity since Terry and Matt's black hair is genetically improbable, given his brown hair and Mary's red hairnote .
- Demoted to Extra: She had less and less screentime as the series continued. She didn't appear at all in Season 3.
- Former Teen Rebel: According to Terry in "Splicers", she had a lot in common with her delinquent son at his age.
- Hypocrite: In "Sneak Peek," Mary initially disapproves of The Inside Peek and tells Terry that it might be "just entertainment" to him, but he'd think differently if he was the one being exposed on the show. When Peek discovers Batman's Secret Identity and intends to expose it on the show, she's suddenly very eager to watch the show, which Terry calls her out on:Terry: I thought you said it wouldn't be entertaining if you were on the receiving end.
Mary: Yeah, well, what do I know?
Terry's younger brother.
- Alliterative Name: Both his first and last name start with "M."
- Annoying Younger Sibling: Although understandably he is very young, and some of his antics could be seen as a coping mechanism for losing his father at a young age.
- A good example of this is one episode where, even being told that the ghost at Hill High is being destructive, he wants to have a seance. The reason? He's scared he'll forget what his father was like and wants to contact him.
- Bratty Half-Pint: Not much to describe since he acts like a standard younger brother to Terry: a sweet, but annoying kid.
- Chocolate Baby: As with Terry, his and his brother's black hair makes it somewhat unlikely that their biological father could be the auburn Warren McGinnis, given their mother's red hair. Fans attribute the McGinnis parents' divorce to this, in part.
- Demoted to Extra: Had less and less screentime as the series continued. Even the comic continuation barely used his character.
- Loves My Alter Ego: Matt admires Batman (a fact Terry wholeheartedly approves of), but considers Terry a boring workaholic who's hardly ever around.