What is the whole history to all the Kingdom Hearts games

Wow. This is going to be long. I'll try to break it down.

Kigndom Hearts follows Sora who wields the Keyblade. His mission is to seal all of the key holes to the heart of whatever world he's at. Along the way, he's searching for his best friends, Riku and Kairi, and looking for King Mickey who mysteriously disappeared. He's traveling along with Goofy and Donald when he finds Riku. Riku is being manipulated and lied to by Maleficent who at this point is the main villain. Riku "goes to the dark side" you could say and assists Maleficnet in kidnapping the princesses of heart. It turns out Kairi's heart was taken and is just a shell you could say. Riku has her and is trying to keep Sora away from her. They all meet again in Hollow Bastion where Riku takes the Keyblade from Sora using dark powers he was granted. Through the power of friendship, he gets the keyblade back and briefly fights Riku. Later he finds Riku again who is actually being controlled by the real bad guy, Ansem. Sora finds out that Kairi is one of the princesses of heart and after a fight with Riku/Ansem, he saves Kairi by stabbing himself with the Keyblade, thus becoming a heartless. Kairi, who is now concious, saves Sora with the power of her heart and she goes to Traverse Town while Sora goes out and defeats Ansem and seals Kingdom Hearts, but he had to seal King Mickey and Riku inside.

Kingdom Hearts: Chain of Memories is next. Sora is once again adventuring around when he first encounters Organization XIII. I'll save you some time and tell you that a girl named Namine puts Sora in a type of sleep which he goes into for two years.

Kingdom Hearts: 358/2 Days follows Roxas who is Sora's Nobody. It shows everything that happened to him and Axel and Xion, who are other Nobodies. And ends when Xion dies and Roxas leaves the Organization.

Kingdom Hearts 2 starts out with Roxas until he finds Sora and Sora wakes up. Then Sora goes out once again to all of the worlds taking down enemies with the keyblad. He's still searching for Riku and Kairi (oh and no one remembered who Sora even was until he woke up again) and the king. This time he must battle the heartless AND Nobodies AND Organization XIII. After all of the fighting and scenes in other worlds, Sora finds the king and Riku. Riku has taken on the appearance of Ansem (only for a short while) and they go to The World That Never Was. Sora adn Riku fight Xemnas, who is the leader of Organization XIII. After he's defeated and Roxas joins with Sora, they go back home to the Destiny Islands. I hope this helped