As complicated as the adoption process is, beginning with the separation of a child from his/her biological parents, it is the responsibility of the new parents and of the adoption agency to allow adopted children the option of knowing their biological parents. There are always severe cases where the biological parents are drug users, abusive, or don't want to be known. Even in these cases it is the choice of the child when they reach a certain age to decide whether or not to know their biological parents.
I think at the age of 18 they should have the chance to find out who their parents are. If they just see it on paper or through a meeting it, it would be enough for me. I don't know how that would play out in the courts,but to me its a must. If the parents are agaisnt it, that should be okay too.
That people keep a child's biological parents information away from them. Even, if it was requested by the biological parents themselves. It is not right and they should pass a law that states children must be given that formation when they are old enough. Unless, no one knows who their real parents are.
If a parent has given up a child for adoption and does not want that fact known and does not want to know the child that needs to be respected or that child might not be allowed to live; however, the child should have access to all facts about the parents including the medical histories.
I do not think that it is necessary to give adopted children the right to know their biological parents. I think that giving kids such a right would cause problems and issues with parents who want to adopt. I think that each case should be left up the adoptive parents.