My adopted brother went from thinking he was an only child to finding out he had a rather large family. He found out through his first adopted mother (long story) and my parents helped him figure out the whys and wherefores...wish I had more information to share, but I don't and can't get any more as he is now deceased. I do remember that it involved interaction with the courts in the city where he was born, but that's about it...and I think his first adopted mother had to give consent or something to that effect. Sorry I can't offer more help.