Organization VI is a group of six powerful nobodies, of which five are from the original group.
When at the first visit to Wonderland, The Queen of Hearts was about to execute Sora using the Dark Keyblade, however thanks to the Chesire Cat, it only hit Sora. But it did create Dark Sora, along with the same time releaseing Roxas from Sora. At that time Roxas and the revived Axel form Organization VI. When the other four were destroyed by Sora and Roxas, originally their personalities roamed which Mickey, Riku, Leon, and Yuffie found. Then the personalities went into their hearts and they let darkness inside and that created four members of Organization VI.
Kindom Hearts III
Their main role in the game is to stop Dark Sora from reaking havoc. They often assist and become playable in certain battles, and split a heartless counterpart of Sora's ally's.
Kingdom Hearts the Deciseive Heartless
Roxas and the rest of the Organization discover Dark Sora alive. For a year they hunt Dark Sora across the Galaxy, until Roxas destroys him at Castle Oblivion.
Kingdom Hearts IV
Their role is rather minor. They don't appear until the first visit to The Darkside of the Moon where they reveal themselves.
Throughout the rest of the series they help Sora and Seth battle enemies.
1. Roxas. Attribute Light. Nobody of Sora
2. Axel. Attribute Fire. Currently nobody of Riku
3. Namine. Attribute Memory. Nobody of Kairi
4. Xion. Attribute Replica. Currently nobody of Mickey.
5. Marluxia. Attribute Flower. Currently nobody of Leon
6. Larxene. Attribute Lightning. Currently nobody of Yuffie.
Originally they were only going to destroy Dark Sora. However they discover that Sora, Seth and their friends are being overwhelmed by Heartless, they begin to help Sora and Seth, which Axel and Larxene call help'n wimps.
Although they mainly where Black coats, instead of black gloves and shoes they where white shoes and have there hands bare.
Althouth their home base was unknown they later turned Treachery/Fantasia into their base of operations.
Though nobodies are'nt suppose to have hearts Roxas claims that they are made of Darkness, which also is light. Though Marluxia can drop it.