Colress was a scientist, who wanted to unlock the full potential of Pokémon. That's why he aided Team Plasma, he needed the funds.

Colress is not a father. Well, he never planned to be a father. But a close friend of his happened to leave her orphaned child behind after an accident, and Colress just so happened to have promised to take care of you, should she pass.

Colress didn't plan to be a father, but here he was. And he'll be sure to raise you well.