hi bellmoore4, i had a similar issue with my sons father, we ended up spliting because he was violent to me, and he washed his hands of our son. 2 years later i recieved a letter from him stateing how much he had changed and how he wanted contact with our son, i instantly went to a soilisitor and they contacted him on my behalf to say that because of the violence and the fact that he had walked away i was not prepared to let him have unsupervised visits and that the only contact he will have for him in the meantime would be telephone contact, until I felt that my son was ready for contact in a contact center etc. My ex got bored of the phonecalls after about 3 weeks and started to demand contact { he only called once a week!] so i said no. Anyway to cut a long story short his father got bored and walked away again. He has also NEVER paid maintenace towards our son.
Your nieces ex does not have alot going for him legally in the sence that
1. he was violent
2. he does not pay maintenance to the child
3. he abandoned his son
He does not have the right to demand access because of the above and if he is serious about regaining contact with the child then it would have to be at the pace of the child i.e regular phonecalls, then gradually building up to supervised visits, then on to unsupervised visits as in a couple of hours on the weekend , and so on and so forth. The ex has really got to prove his worth. It will be a long process because at the end of the day you have to concider the childs feelings and like you said the child is settled and calling someone else daddy. please get this all done via a solisitor as if it ever went to court at least you can say youve done it all above board and its all on paper, that way if he breaks the contact agreement, at least you can say to the child when he/she is older that you tried to resolve the matter. good luck xxx