My dad was adopted. He found his birth mother who didn’t want to know him. Years passed and he thought she had probably died so he went in pursuit of finding his half brother and sister. He found them and they welcomed him with open arms. They knew nothing of their mothers past but they were happy that they had found my dad coz it explained lots of oddities about their mother. Sadly they lost my dad pretty much as soon as they found him as he passed away. We all stay in touch with them though. Its nice to have found uncles aunts and cousins :)
Similarly my ex’s mum annouced one christmas that she had another son who she gave up for adoption. She had kept it secret for many years only to be forced to tell when he came looking for her. Her other 2 sons accepted him.