User blog comment:Mrgjman/700- What we don't know/@comment-6883921-20130302075135

Since Dofy was at the site where Ace was killed, it's likely that the Mera Mera no Mi was the one he found; he was one of the few to actually stay at the battlefield after the war (by trying to kill Moriah).

Also, since Dofy went as far as quitting the Shichibukai to retrieve Ceasar, it's very unlikely that he can make DFs himself, much less Logias.