2 LAST NAMES!?!?!

Micah
Is it stupid to give your baby 2 last names? My sons father is in my life...but we've been on and off for over 5 years. He already has a son with his last name. He will be PISSED if I don't give baby his last name, and may refuse to help me financially after baby is born and I am unemployed until baby is atleast 6 weeks. There is also nobody to carry on my last name. We are are all girls. So ny last name will die out soon. So I am thinking of giving him both.