Ok here's my theory about Sora and BHK. See when Sora in Hollow Bastian became a heartless and consumed by it. IT was like he was a zombie. Then he remembered of having feelings of her and memories deep deep inside. So when he became a heartless his light side was in another dimension (light or dark) Twilight or something. So it came back and he was back to himself. But when he came back its like there is another him. BHK. he looks like him though. But he wears white clothing and stands at Twilight Town... So maybe BHK might be Sora in another way........