Kai

Kai was Sora's older brother. He was older than Sora by two years. He grew up with Sora on Destiny Islands, but when it was destroyed by the Heartless he lost his heart and became a heartless. He has a nobody named Mizu (whose name means water in Japanese) who is a member of Organization XIII. At the end of Kingdom Hearts II when Sora returned to Destiny Islands his brother was there alive and well (and not a heartless). It is unknown why.