I dread the day my son turns 18 because I fear he will want to meet his biological parents. That's selfish but true.?

Discuss with him. Not knowing how old our son is is hard to give advice. Does he know that he is adopted? If so have you put a positive spin on it? Is it fear that he has discussed it? What do you know of his biological and what was the reason? There are questions I would have to know and then I could answer completely. If you have been frank with him it possibly will not matter whether he meets them.