元朝秘史
According to "The Secret History of the Mongols", Shikhikhutag was a son of a Tartar nobleman. As a child, he was lost during a skirmish between the Mongols and the Tartars in the early 1190s and was discovered by Genghis Khan's men later. He was brought to the khan's mother, Hoelun, and was adopted by her as a son.