One Piece fans have theorized about Joy Boy and his connection to Luffy for years now. Arguably, the most popular theory was that Luffy is Joy Boy reincarnated. It's a controversial theory among fans, as many hate the idea of Luffy's character falling under the Chosen One or Child of Prophecy tropes like many other protagonists do. Fortunately for everyone, this is not the case with his Devil Fruit playing a key part in explaining how he is connected to Joy Boy.
Source：https://www.cbr.com/one-piece-luffy-devil-fruit-true-nature/
