Shahr Bano's immediate family

Source Wikipedia:Yazdgerd's daughter Shahrbanu is believed to be the wife of Husayn ibn Ali.Yazdgerd III (also spelled Yazdegerd, Yazdiger, or Yazdigerd, Persian: یزدگرد سوم, "made by God") was the twenty-ninth and last king of the Sassanid dynasty of Iran and a grandson of Khosrau II (590–628). His father was Shahryar whose mother was Miriam, the daughter of the Byzantine Emperor Maurice.[1] Yazdgerd III ascended the throne on 16 June 632 after a series of internal conflict.Yazdgerd was born in central Iran, Yazdgerd III reigned as a youth and had never truly exercised authority. The Muslim conquest of Persia began in his first year of reign, and ended with the Battle of al-Qādisiyyah. Yazdegerd sought an alliance with Emperor Heraclius, who was an old rival of the Persian Empire.

Following the battle of al-Qādisiyyah, the Arabs occupied Ctesiphon, and the young King fled eastward into Media going from one district to another, until at last he was killed by a local miller for his purse at Merv in 651.[2]

The legend is that he was killed by a miller who robbed him of his clothes and jewellery, but there is a strong suspicion that the governor of Merv, was the real culprit [3]

Ferdowsi a contemporary of Mahmud of Ghazni recounts the killing of Yazdegerd by the miller at the behest of Mahuy Suri
“ Mahui sends the miller to cut off his head on pain of losing his own, and having none of his race left alive. His chiefs hear this and cry out against him, and a Mobed of the name of Radui tells him that to kill a king or prophet will bring evil upon him and his son, and is supported in what he says by a holy man of the name of Hormuzd Kharad Shehran, and Mehronush.

The miller most unwillingly goes in and stabs him with a dagger in the middle. Mahui's horsmen all go and see him and take off his clothing and ornaments, leaving him on the ground . All the nobles curse Mahui and wish him the same fate.[4]Yazdgerd's son Peroz II fled to China. Yazdgerd's daughter Shahrbanu is believed to be the wife of Husayn ibn Ali. Yazdgerd's other daughter Izdundad was married to Bustanai ben Haninai, the Jewish exilarch. The Bahá'í religious leader Bahá'u'lláh's ancestry can be traced back to Yazdgerd III.[5][6]
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