Key of Heaven

But even so, I am confused. in the Awakening, we know that the voice is Sora, but says "his newborn heart," and then at the end of the game Ventus said that "their hearts have a part that is not enough, born at the same time." First of all there is to know the time it Ventus been training with master Eraqus. or that Nomura said in the Uiltmania of KHBBS to explain more about the connection between Sora and Ventus.