Flint first showed up in Pewter City selling rocks as souvenirs, where he met Ash and Misty. When Ash started bragging about becoming a Pokémon Master, Flint shut that down fast—told him he had no shot against Brock, the local gym leader. He was right. After Ash lost the match, Flint took him home and filled him in on what was actually going on with Brock: the kid was stuck raising nine younger siblings because their dad abandoned the family to chase his own trainer dreams and never came back. Their mom disappeared too.
Flint ended up helping Ash prepare for a rematch by jacking up Pikachu's power at a hydroelectric dam. Then came the reveal—Flint was Brock's father. He'd failed as a trainer and couldn't face his own kids, so when Brock decided to travel with Ash, Flint finally stepped up and took over running the gym and the household. The whole thing was pretty rough.
Things got awkward when Brock came back through Pewter City after traveling Kanto, Johto, and the Orange Archipelago. He called his dad out for letting the gym fall apart. Flint got embarrassed trying to explain himself, especially when Brock's mother Lola suddenly showed back up and had redecorated the whole place. Flint hated it so much he just shut the doors.
Lola challenged Flint for the gym leader title and beat him, but Brock managed to take down his mom. They all agreed to rebrand the gym as a Water and Rock-type hybrid, which seemed to smooth things over. Oh, and Flint had given Brock his first Pokémon, an Onix, as a birthday gift way back.
Content compiled by AnimeList.moe from publicly available sources.
