How much does it cost to change your last name?

My boyfriend and I are getting married. His mom remarried when he was a baby and never changed his last name. He wants me to take his family's name but I only want it if he takes it as well. How much would it cost to get his name changed in Texas?How much does it cost to change your last name?seriously, this is not the right place to ask a question like that.especially if your really going to do it. Call social security and ask them not people.