Baby daddy not around my pregnancy but wants baby to have his last name?

My baby daddy has me blocked off everything, for no reason. He hasn’t helped out or checked up on me this entire pregnancy, but the last I heard from him he told me he wanted a dna test and that the baby will have his last name or he will take me to court. I’m just confused. He’s shown no signs of stepping up as a father but expects me to give my child his last name?? I already have a son and he has my last name. His dad isn’t in the picture and he wasn’t in the pregnancy either. I’m so glad my son has my last name. Instead of some stranger he might never even meet. Am I wrong for wanting to give this baby my last name too??