Everyone says Sora was just a floating heart, but where's the source? Is it in Jiminy's Journal from KH2 (I don't have KH2 anymore, traded it for KH1)? That would clear up a lot of confusion, at least for me.
Also, if that much is true, and Roxas was Sora's body and soul, why could only Sora see Roxas during their encounter at The World That Never Was? If Roxas had a body and soul, Donald and Goofy should have been able to see him. In fact, Sora should have been the one who went unseen - thought that's impossible because he's the protagonist.
On a related note, if Roxas is indeed Sora's body and soul with Ven's heart, he isn't a Nobody - regardless of how he came into "existence". There are specific criteria as outlined by Ansem the Wise that define Nobodies, the most prominent of which being they DON'T possess hearts. This goes as far as to say that Xion wasn't a Nobody either, "special" or otherwise. She was just a puppet with a heart. Namine, on the other hand, is a "special" Nobody due to her lack of heart and the circumstances surrounding her coming into being, circumstances which I myself am not totally clear about.
Firstly, No matter how you say it, the reason why Roxas exists is because Sora's heart left his body and his body and soul acted on their own. This being is called a nobody. Just because he has something other nobodies doesn't have doesn't make him an entire different species all together.
Secondly, Sora's heart left his body and his body and soul went to Twilight Town and formed his nobody. This nobody was given the name Roxas. Ansem the Wise wrote what standard nobodies were and how normal nobodies are made, but he is stumped by Roxas and Namine. In the end of KH2 he's realized that there are things he has yet to understand about everything he thought as fact. Roxas was created the same way a nobody is but he is different in the fact that even though Sora's heart left his body and soul, he somehow has emotions and feelings and is hinted to have Ven's fractured heart. He isn't the same as the rest just as Namine is but he is still a nobody all the same.
Thirdly, Xion didn't come into existence as a nobody would. you are missing the point. Yes not having a heart is a sign of a nobody but they come into existence through a specific and perculiar method that Yen Sid, DiZ, and others have pointed out. If a strong heart leaves the body, and the body and soul animate and come to life on their own, they are a nobody. The shell of the person they once were. Xion was created as you even said yourself, as a puppet. Created in a lab, experimented on, and given a specific task to do. Riku Replica is not a nobody he is a replica. Xion is not a nobody she is a replica. She was not created by someone heart leaving a body. No heartless was made to accompany with a nobody. She can't be a special anything she doesn't classify under.
Fourthly, If Roxas, Sora's nobody, therefore having Sora's body and soul that means Sora has all that is left of the heart, soul, and body combo. Which is the heart. Kairi restored Sora's heart to him when he was a heartless when she hugged him. Giving him his form back but not his body and soul seeing how uhm Roxas is still in existence and using it.
And lastly, Roxas and Sora's fight was internal. Sora got his body and soul back when Roxas went back to Sora in the beginning to KH2. what is left of Roxas was triggered by Axel's death and challenged Sora to an internal struggle. Evidence? they fought in the station of Awakening which is located within the heart. Roxas was still doing this while inside Sora. He cried when he left Twilight Town. He held the blue orb thing through Sora with the others, he's still there but not in the physical plane. It was an internal struggle. Anything else you want me to point out?
