My stepson was born in France, he is 22 years old his mother is french and his father is an american an lives in the U.S.A. My stepson lives in France but wants to seek dual citizenship IF POSSIBLE?? Who should he ask for that and what kind of documents are requested... He might want to work in the United States in the future ans would really like to be French and American... We heard that after 18 years old you have to choose between the two nationalities... is it true? Thank you very much.

Call up the INS. If he is adopted you may have some problems, however, I had a German friend who came to live in the states, he was granted citizenship based on the same premise. His father was American.

Green card | Green card Application | Greencards Process

Check the link out. It has a ton of useful info.

Good Luck