March 1 (Reuters) - A grandson of Ayatollah Ruhollah Khomeini, the late founder of the Islamic Republic of Iran, is likely to figure prominently in the deliberations of the clerics who will determine who replaces Ayatollah Ali Khamenei as Supreme Leader.The killing of Khamenei, 86, in a U.S.-Israeli attack has brought new urgency to the question of who will be the next Supreme Leader, a long-simmering issue over which there had been no clarity despite his age.