Offspring should have access, if available, to the medical backgrounds of their family. So many medical issues run through the lines of heredity. It is only fair to give families this information. If biological parents will not release this information or, if it is unknown, there is not much that can be done. If the information is available, it is really only humane to pass the information along.
Children who are put up for adoption have the right to know the identity of their parents for medical purposes. If a parent has a dangerous genetic disease or condition, the child has a right to know about this. Knowing about a latent condition could help this person to make lifestyle choices that could save their lives.