Replica Program

The Replica Project was a planned series of experiments conducted by Xemnas. He attempted to make replicas of Sora in the event that the original proved to be useless to his plans for Kingdom Hearts. However, after the death of Xion ("No. 1") and her subsequent absorption by Roxas, Xemnas discontinued the project. Since Xion is replica No. 1 this could mean that there are more replicas of Sora or Riku.