Some of you may remember that I work with DD and SED boys (developmentally delayed and severely emotionally disturbed). One of my boys, who is 15 right now IIRC, was adopted when he was very young by his aunt. He doesn't yet know that his "aunt" is his real mother, this is regarded as their family secret. He was adopted by his aunt so they could flee from mexico to the united states.
We are currently working on ways to tell him about the family secret. If I were to tell him right now, just go up and say "hey man, your "aunt" is your feal mother and your "mother" is really her sister", he would have a breakdown, and slip well beyond our ability to help him. I would be willing to bet that he would go AWOL and probably hurt himself or someone else. He has some real issues with abandonment and if he learned that he himself was really abandoned, he would crack.