Ichiru Kiryuu

Zero's younger twin brother. When they were younger, they were both taught by Touga Yagari, though Ichiru did not seem to share Zero's natural ability because he was sickly. Zero and Ichiru were very close as children, although later Ichiru claims to have hated Zero after overhearing that his parents preferred Zero over himself. Ichiru now has been cured due to drinking Shizuka's blood and has appeared at Cross Academy as a student by the orders of Shiki's father. Wikipedia