Sartaq Khan

Sartaq (or Sartak, Sartach, Mongolian: Сартаг, Tatar: Сартак) Khan (died 1256) was the son of Batu Khan and Regent Dowager Khatun Boraqcin of Alchi Tatar. Sartaq succeeded Batu as khan of the Golden Horde.
In 1252, Alexander Nevsky met with Sartaq at Sarai. Alexander received yarlyk (license) to become Grand Duke of Vladimir in vassalage to the Kipchak Khanate. According to Lev Gumilev he became Sartaq's anda (sworn brother, probably akin to blood brother) and an adopted son of Batu Khan.
His reign as khan of the Golden Horde was short-lived. He died in 1256 before returning from Great Khan Möngke's court in Mongolia, less than one year after his father, probably having been poisoned by his uncles Berke and Berkhchir. Sartaq was succeeded by Ulaqchi briefly in 1257, before his uncle Berke succeeded to the throne. It is not clear whether Ulaqchi was his brother or his son.
Sartaq's daughter Theodora (or Theothiure) was the wife of Gleb Vasilkovich first Prince Belozersky of Beloozero and Rostov, a grandson of Konstantin of Rostov and first cousin once removed of Alexander Nevsky. Their descendants include Ivan IV of Russia and innumerable families of Russian nobility.