Mojtaba Hosseini Khamenei, the second son of former Supreme Leader Ayatollah Ali Khamenei, has been named Iran's new supreme leader, Iranian state media reported Sunday. While the new supreme leader has never held elected office, the 57-year-old for years has operated quietly behind the scenes from within his father's office — cultivating influence across the security establishment, particularly within the Islamic Revolutionary Guard Corps.Mojtaba Khamenei was selected by Iran's Assembly of Experts, comprised of 88 clerics and supervised by the 12-member Guardian Council, which acts as a watchdog for Iran's constitution. Ali Khamenei was killed on Feb. 28 in a strike that also took out about 40 other high ranking Iranian officials.When his father became supreme leader in 1989, Mojtaba Khamenei effectively became one of his closest aides.…