My question involves name change laws in the State of: Philadelphia

I have two children with a man who is Muslim and I am not. When I had my children I gave them their father's last name. He wanted them to have a Muslim last name like his older son. We came to a compromise where I hypenated their last name with his muslim name although its is not legally his last name. He promised me before they started school he would have his last name legally changed to his muslim name. Its been six years and he hasn't made one attempt to change his name. Now my poor children are walking around with their father's legal last name and a muslim hyphenated name which isn't legally their father's. I want to drop the last name because it doesn't belong to either of us but their father is against it. Can I legally drop their hypenated name without their father's permission if it doesn't appear on his birth certificate?