I think - and this is just an opinion - that the worst age to tell a kid he is adopted is when he is on his teenage years. Okay, maybe from puberty until he finishes his teenage years. Why? Because this is the age a person who doesn't have complications in himself is so con*sed of what he is. This is the "I'm not a girl, not yet a woman" stage of a person's life. You can break the news either before or after that.