William Thomas "Tom" Riker was a clone of William Riker created at Filo Kamino, genetically indistinguishable from each other, with personality and memories identical up to the point of the duplication. One of the duplicates continued to be known as William Riker. The clone himself chose to use his middle name and be known as Thomas Riker. Thomas and William clashed almost immediately due to the resentment each felt towards the other. They changed the memory and personality by Taun We after the war.