Izuna Uchiha

was the younger brother of Madara Uchiha, who was known as the strongest Uchiha. He bears a striking resemblance to Sasuke Uchiha.

Background
Eighty years prior to the start of the series, Izuna and his older brother became the first Uchiha to awaken the Mangekyo Sharingan. Madara used the power of his Mangekyo Sharingan to take control of the clan with Izuna at his side. When Madara eventually went blind, he took Izuna's eyes to regain his sight. Itachi Uchiha suggests his eyes were taken by force, but Madara insists Izuna willingly gave up his eyes for the good of his brother and the clan. According to the third databook, Izuna later died in battle.

Abilities
As the younger brother of Madara Uchiha, the strongest of the clan, Izuna himself was said to have been equal to his brother in every way. His Mangekyo Sharingan, developed some time after Madara, took the appearance of three bars stretching out of his pupil. When Madara took his eyes the two's Mangekyo combined.

Trivia

 * is the name of a wind spirit, and can be translated as "rice-rope".
 * Izuna shares a birthday with fellow Uchiha Obito