A sister of Iran's Supreme Leader Ali Khamenei has condemned his crackdown on nationwide protests and called on the widely-feared Revolutionary Guards to lay down their weapons, according to a letter published by her France-based son.  Iran has been gripped by unrest since the death of 22-year-old Kurdish Iranian woman Mahsa Amini in police custody on Sept 16., and is facing a three-day general strike movement which started on Monday.  Badri Hosseini Khamenei, who resides in Iran, criticized the clerical establishment starting from the time of the republic's late founder Khomeini to her brother's rule, the letter, dated "December 2022", said.  "I think it is appropriate now to declare that I oppose my brother's actions and I express my sympathy with all mothers mourning the crimes of the Islamic Republic, from the time of Khomeini to the current era of the despotic caliphate of Ali Khamenei," she wrote in the letter which was shared on Wednesday by her son Mahmoud Moradkhani's Twitter account.  "Ali Khamenei's Revolutionary Guards and mercenaries should lay down their weapons as soon as possible and join the people before it is too late," the letter said.  The Revolutionary Guards are Iran's elite force which has helped the country's establish proxies across the Middle East, and runs a vast business empire.  In November, Khamenei's activist daughter Farideh Moradkhani was arrested by authorities after calling on foreign governments to cut all ties with Tehran.