X2 was a Force-sensitive Clone Trooper who had been cloned from the DNA of Jedi Knight Falon Grey.
Along with his brother, X1, the two participated in many key battles during the Clone Wars beside their Jedi General, Ferroda. When Order 66 was issued the two brothers killed Ferroda but X2 felt it was wrong.
X2 doubted their decision and later defected to the Rebellion. It was later that he learned of his heritidge and aided his father on Dantooine. However Grey soon came to face X1 and the was slain by his other son.
X2 continued to fight in the Galactic Civil War, learning the ways of the Force from Luke Skywalker. After the war's end X2 was elevated to the rank of Jedi Knight and learned that his brother, now a self-proclaimed Sith, was planning on re-building the Empire. When Luke was captured by X1 and taken to Mustafar X2 set out to stop his brother once and for all.
X2 met his brother and engaged him in lightsaber combat. Proving to be the stronger of the to, X2 struck his brother down but refused to kill him. Sensing that X1 was attempting to use the Force to manipulate his lightsaber and kill X2, he jumped aside, resulting in his brother impailing himself with his own blade.