My son his 5 years old, he has both my last name and his father's last name. His father and I are in dispute, his father is from puerto rico, our dispute is, he says that since I placed both last names on the birth certificate, his last name isn't our son's last name. The names aren't hyphenated either on the birth certificate. In the state of Florida what ever the last name is, is that the child's legal last name?
For example let's say my last name is Blue and the father's last name is Red, birth certificate says " Jamie Joe Blue Red" What is the legal last name in the state of Florida?

His legal last name would be Blue Red. The same as mine was before I dropped my maiden name when I was married. Well not those names exactly but both words are the last name. I just droped my maiden name this last September when I renewed my license again so am back down to one word last name.