i think that terra might have been kinda brain-warshed like riku did by maleficent and maybe he fell into darkness more and when he was in the battle with master xehanort he lost his momory and when ansem
foundn him the only thing he remebered was the name "xehanort" and when terra died he was zemnas. thats why he called aqua old friend.
this is awesom stuff i think maybe awua is #14 and that black knight may be the gaurdin of xehanort in kh1 but thats a long shot terra might be played like sora, aqua like donald and ven like gofy