My ex wife recently revealed that the youngest born (who is now 4 years old) is not my son. We've been separated for 5 years but we are not yet annulled legally although she's living with the son's biological father (who is also married and not yet legally annulled).
When she got pregnant I paid for the hospital bill because I wanted to help her although I already knew that the child is not mine. I was confused at that time on what to do. Although I didn't sign anything at the hospital for the child's birth certificate, I know that it was automatic for the child to use my surname since legally speaking the mother and I are still married.
I want the child to change surname (remove my name and surname in his birth certificate) is this possible? How long is the process and shall I need evidences to prove the child's paternity?
What if the mother agrees and confess that the child indeed is not my son, will it lessen the process?