One Piece: What If We Knew the Future?

In this story, Luffy and Nami are siblings, and Whitebeard's grandson and granddaughter. Blackbeard is discovered while preparing to kill Thatch, so Thatch survives and Blackbeard escapes. Ace isn't captured, Sabo has regained his memories, and the three brothers reunite. Ace and Sabo happen to be aboard Luffy's ship when a screen appears in the sky. The people chatting on the screen are talking about how Luffy has already become the Pirate King. Zoro ends up with Nami.

Theme: Change a tragedy.