In the spring of 1171, Yesugei-baatur decided to travel to Eastern Mongolia to ask Hoelun's father for her hand. He took his son Temüjin, then nine, with him.
While returning home after negotiations, Yesugei stopped off at a Tartar village. While there he was poisoned, in either his water or his food, and died around midnight on 31 March 1171. The most common hypothesis is that the food or drink was poisoned by the Tatar chieftains because they were afraid of the strength and power that the future Mongol Empire could attain under Yesugei's leadership.
According to "The Secret History of the Mongols", after Yesugei died, his wife Hoelun "became the head of the household, and with great hardship raised her six children, among whom Temüjin was eldest".