Is the unmarried mother committing fraud by adding the assumed father to the birth certificate?

After 21 years, the "father" is now finding out that he was listed officially as the father of the son. He was never married to the mother, nor did he sign any paternity documents. He never lived with both son and mother ,so he never had access to any of the boys documents. He currently (and always ) supports the son, but the mother is using deception and the court to further extort more from the father. This is part of an ongoing court matter to show the character of the mother and son