Surprisingly, Jason was the best parent out of the seven. Eight years after the Giant War, when Nico Grace was born, it was obvious that he favoured Jason over Piper.
When Nico grew older, Jason was the perfect balance between the strict, and free reigning parent, he figured that was from being brought up in the legion. He'd never had a childhood, so he wanted his son to have the best life possible, but at the same time, the Roman in him wanted Nico to be perfect in every way possible, resulting in the strictness.
But the main reason for the son of Jupiter's amazing parenting skills: he wanted his son to have a happier life than his namesake, who'd sacrificed himself in the Giant War to save Piper.