Vistahm and Vinduyih deposed their brother-in-law Hormizd IV, King of Kings of the Sasanian Empire. Vistahm: Vistahm or Bistam, was a Parthian dynast of the Ispahbudhan house, and maternal uncle of the Sasanian king of kings of Iran, Khosrow II. Vistahm helped Khosrow regain his throne after the rebellion of another Parthian noble Bahram Chobin, of House of Mihran, but later led a revolt himself, and ruled independently over a region which encompassed the entire Iranian East until he was defeated by Khosrow and his allies. February 6, 590. Wiki link