Who is Mojtaba Khamenei, frontrunner to be Iran's supreme leader?

"He has strong constituency and support within the IRGC, in ​particular amongst the younger radical generations," said Kasra Aarabi, head of researching the IRGC at United Against Nuclear Iran, a U.S.-based policy organisation. "So if Mojtaba is alive, there is a ​high chance that he will succeed (his father)," he said, describing Mojtaba as already operating as a "mini supreme leader".