How young can you be and still be considered a child predator?

Question is inspired by a good friend who told me his cousin abused him. The older cousin was around 11, which would make him a child predator while he was a child himself. It made me wonder if there’s a power limit. If a three-year old acts inappropriately with his infant sister, that’s not predation, it’s a child who doesn’t know better … righ? How young can you be and still be considered a “predator”?