*Spoilers* if you want to understand MY hypothosis read all 26 Ansem Reports: .com/wiki/Ansem_Reports . This will be very confusing if you don't.
What if the expieriments in Kingdom Hearts were real? Some religons believe in reincarnation. In Hinduism, it is believed that one would die and come back as a person, animal, or vegitable. Karma would place said person's soul into the appropiate category. Good Karma would be a human. Middle Karma would be a animal. Bad Karma would be a vegitable. What if there were a Very Bad Karma? Would that put you into a Heartless? Think about it: people have referred to each other as "heartless" before. Everybody has done something mean or bad at least once in their life. There is truely darkness hiding deep in people's hearts. Kairi is referred to as one of the Seven Princesses of Light. I would personally like to know about the other six and how they came to be. Ansem wrote that everybody has darkness in their hearts. If Kairi has none, then she -according to the reports- is as perfect and pure as Jesus Christ. If she has no darkness in her heart, then how was she born? How is it that she has only light in her heart yet no-one else does? It also explains about how Namine is a special Nobody. Nobodys are special Heartless themselves but Namine is Kairi's Nobody. I think that shadows are caused because Darkness is scared of Light. Shadows are caused when the Darkness is Hiding from the light. Go into a dark room and turn on the light, all the Darkness will run for cover. So in the reports, it says that Namine was created because Kairi's heart transferred some of the darkness from Sora's heart. But, when listening to my thought of darkness, wouldn't the Darkness in Sora's heart have ran from the Light of Kairi's heart? And is Sora's heart all Light now bacause the Darkness left to create Roxas?
I will be putting more notes on the Ansem Reports on the site. Feel free to ask any questions or correct any erorrs or misunderstandings I may have.