Hi C., My personal opinion is to not change his name, that should be an adult decision that he makes as an adult, being a male child, if you change his name, he will never be able to carry on the name of his father (birth father). My neice was 7 years old when my brother married her mother, she is now 20 years old, last father's Day to my brother's surpirse he was called into court, and my niece's fathers day gift to him was changing her last name from Villa, to Covington, she made an adult decision, paid for it herself. You want your x to pay child support because he's your sons father, but want to take his name away, i don't think that is fair, when my brother came into the lives of his now wife and her 2 kids, he bacame their dad, physically, mentally, emotionally, and financially, my niece was 7, my nephew was barley 2, their dad was way behind in child support, my brother's heart was this is my family now. and that was it.
Let your son make that decision when he is an adult, you mentioned your son is the only one with a different last name, that's what happens when you blens families, My nephew is the only one with a different last name, when he's an adult he may decide to change his name, or he may decide to carry his birth fathers name, but it will be his choice. J. L.