“Can my son have his daughter’s last name change to his last name? His daughter lives with him and she hasn’t seen her mother in 7 years. His name is on the birth certificate as the father.Will doing this have to go through the courts?”

I’m going to answer under California Law. Name change proceedings are handled through the Probate Court. As the parent your son would be the person to file the petition on his daughter’s behalf. Besides the filing fee, usually the biggest expense in a case like you are describing is service of the petition on the other side. If he does not know where baby’s momma is, then service would generally have to be by publication. As far as I can tell though, it’ll have to go through the Courts. There’s plenty of self-help stuff on the interweb, and depending on the jurisdiction this process can be fairly simple. If he’s struggling with it, of course most general practicing attorneys would be able to figure this one out.