Kingdom Hearts history - One of gaming's most complicated stories explained
GamesRadar - Preparing to dive into Kingdom Hearts: Dream Drop Distance? Don't leave your home world without our spoilerific guide to Sora' Disneyfied quest.
(Kingdom Hearts, Nintendo DS, PS2)
The story isn't complicated for me. Pretty straight forward if you stay with it, but I can see where people might get confused with the games releasing on multiple different platforms and all. The story is really engaging as soon as you understand it. My favorite story in the series is Birth By Sleep. I wish they just released three games (1, Re:CoM, and 2) as an HD Collection though, so the current generation can understand it more.