They lied to their DD and never told her she wasn't DH's biological daughter. They changed the birth certificate to name him as the father and DH's ex never intended to or wanted to tell her the truth. A couple of years ago, DSD asked her Mum outright if DH was her real father and her Mum said of course he was, where on earth had she got that idea from.
All extended family members have known about this for years and it was highly likely DSD would find out at some point. She has now confronted her Mum again and said she knows for a fact DH is not her birth father, after reading some papers her Mum had in the house saying as much apparently. Dh spoke to DSD last night after her Mum rang and DSD didn't even mention it at all and DH didn't bring it up, they both just chatted like she didn't even know!!!
DH and his ex are both 'sweep it under the carpet' types as is DSD, but she has a history of self harm and eating disorders and I am now very worried about her but feel there is nothing I can do to help in any way. I have suggested that DH goes to see DSD to discuss immediately after work today, but he won't go until Monday, combining with with a work trip! His ex hasn't done anything except cry it seems and I feel they both, but particularly DH, should be doing more to help their DD come to terms with this.
DSD is 21, BTW.