MIL had 3 sons(including dh) with dh's father, who she worked with and had known since she was in her early teens. They had a relationship lasting over 15 years and he was a couple of decades older than she was. This man was married and had 3 teenage children with his wife when dh and his brothers were born so I can only assume he was living a double life as dh says he remembers his dad living with them but he never left his wife either because he didn't want to do it while the children were still at home. DH's birth certificate even has some random reworking of his father's name in the "father" section because MIL and dh's father were so keen to keep their relationship secret.
DH's father died when he was a small child and his wife became aware (or may have already been aware) of his other children. DH and his brothers were not invited to his funeral and their names are not on his headstone, although his elder 3 children's names are (so we know what they are called).
Fastforward 20 odd years and I was in a beauty salon when I noticed the name of the woman doing my nails had the same name as one of dh's half sisters. (it's a small town and her first name is not very common which is why I think it's her, although I don't have any proof).
I mentioned it to dh and basically he hasn't got a clue what to do about it. He has always said he would love to meet his half brother and sisters, mainly because he would like to ask them about their father as he has so few memories about him. However, although we know that dh's father's wife knew about dh, we don't know if their children were ever told.
So dh is in a position to potentially contact his sister but we don't know whether to do it or not. I think if we did contact her a letter would be best but he is scared of how they will react.
It's such a horrible situation because none of this is dh's or any of his siblings fault and they can't help who they were born to.
What does everyone think we should do?