Luffy's Twin Sister

This story is about Luffy and his twin sister, how they have stayed together their whole lives, and all the interesting voyages they have been on.

There's a little twist, they split ways when they're 12 and meet up again when they're 17 with their whole crew; Luna wants to become Queen of Pirates and Luffy wants to become King Of Pirates. They've both eaten Devil fruits. The question is who will come out on top...

Read for the answer.
PS: I do not own one piece or its characters, just writing a story based off it.