So, Xion is a puppet created from Sora’s leaking memories by Xemnas. She resembles Kairi because of Sora’s strong memories of her. Then when Roxas defeats her, he absorbs her and is thus able to dual wield keyblades. Thus being why Sora can dual wield when Roxas is willingly absorbed by him.
Just…no. It sounds very stupid. However, were I describing that Roxas is the body & soul of Sora, born when he lost his heart to the darkness by choice. Or that Naminé is born of a blend of Sora & Kairi’s body and soul when Kairi’s pure heart restored Sora and is able to mess around with the memories of Sora and those close to him (i.e. party members, Riku, Kairi). These things do sound foolish in practice, but when you’ve played through, they do make sense.
Then, I learned that at some point, Xion (being created of memories and taking on many different forms) appears as Ventus from Birth By Sleep, which always seemed like the more interesting game to me. So now I’m pondering on how Sora, Xion, Kairi or Xigbar (who sees her/him as Ven) is/are related to a Keyblade Master of ten years past before any half of them even existed (Sora & Kairi were just kids, with Kairi still being at Hollow Bastion).
If you’re not confused, congratulations, you know your Kingdom Hearts stuff.