My 4 year old son has his father's last name and he has basically abandoned this child. And he will not give up rights and is not authorizing a last name change. Is it okay for my son to go by my last name in school? I understand that on legal documents he must go by his legal last name. It's very difficult for me when my son asks why me and his sister have the same last name.. he feels so left out and gets depressed.