There are a a few problems with the whole Xion is Kairi's Nobody theory, and one of them is the fact that KH2 exist. In KH2 we see Namine fuse with Kairi at the end. This pretty much establishes her as Kairi's Nobody. The other problem we have come to is where you say Kairi made a Nobody when she lost her heart. The fact that we see Kairi's Body in KH1 on Captain Hooks ship and in Hollow Bastion means she couldn't have created a Nobody when she lost her heart.
i dont see the flaw, since this takes place before kh2, what if xion fused into kairi a long time ago?
and kairi lost her heart twice,
the first time she lost from her own body, and the second was her lost was removed from sora.
and its not necessarily true about the body existing, since roxas and sora existed at the same time, and namine and kairi existing aswell. if nobodies are the bodies (which i dont believe) how come sora has two bodies? and how come kairi has two bodies aswell?
and if u include xion aswell, that would equal 3, but we arent sure yet