User blog comment:TakoyakiMan/Garp's Other Half/@comment-1984061-20110510175540

I think Luffy's mom is Garp's daughter, and that Dragon married her and decided to take the name Monkey the same way Ace took the name Portgas. As Dragon doesn't look like either Garp or Luffy whom both look alike. Another theory that would go nicely with this is if Dragon was originally a Gol.