I have it on good authority to believe that it is Xehanort in his youth. After reading the Xehanort (he is not a master yet) reports - http://forums.khinsider.com/spoilers/141407-spoiler-section-rules-read.html - (thank u Raz on that one) and watching - YouTube - Kingdom Hearts Birth by Sleep Playthrough part 1 (beginning) . I learned that Xehanort was origionally from Destiny Islands and traveled the words and well if u read the reports and watch the video
you'll put the pieces together.

^^^* NOTE: BE SURE TO READ THE SPOILERS FIRST!!!!!!!!!!!!!!!!*^^^