Roman Law
There is an interesting point in Roman law that I learned about some years back. Apparently, under Roman law, a parent could disown a child only if that child was biologically theirs. If the child was adopted, it was actually illegal to disown the child. This makes sense, if you think about it: you do not get to choose the children you give birth to; you do deliberately choose the children you adopt. Therefore, the choice ought to be binding. Thus, according to Roman law, if you adopt a child then, no matter what that child grows up to be, no matter what they do, they are yours.