My sons dad has never been in his life, my son is 5. His biological dad has recently started paying maintenance but is all dealt with through his mum, she doesn't see my son either. My partner has brought my son up since he was two and he calls him dad. Me and partner also had a daughter together and are engaged. I want to change my sons name to my partners but was wondering do I need to inform his biological dad? He has absolutely no interest in him and isn't on his birth certificate!