The body, soul and heart are reunited and they're a person again. [His tone is an apologetic one because he knows this is a lot. He's so sorry, Zack.

Sora takes in that explanation of the Lifestream slowly, rolling it around in his head before he makes a thoughtful sound.]

Yeah that does sound really similar to what Kingdom Hearts is. Maybe they're connected some how! I mean, all worlds are connected in some way, even if you don't know the others exist.