Yes it is. Portgas D. Ace. He was known as "Fire Fist Ace" back home.

[He chuckles, remembering how silly the name seemed but also how it suited the brother. The fact that he knew it before he regained his childhood memories.. it was pretty surreal.]

You look really lovely. The hat compliments your attire. [Sabo gives a nod to Momo and widely grins. Perfect hat ensemble to go with the woman's outfit. Definitely a plus.]