After Yesügei's death, Toghrul initially helped Temüjin in arranging his marriage to Börte and uniting the tribes, but later defected to Genghis' anda and rival, Jamukha.
The Secret History of the Mongols records that he was poisoned by Tatars while sharing a meal at a wedding[3] on the way home after leaving Temüjin at the home of Dai Setsen, a noble man of Khongirad tribe, when two fathers, Yesügei and Dai Setsen, agreed that their kids, Temüjin and Börte, would marry.
The Secret History explains that he wanted to join their feast, but he knew he could not reveal his identity since he was known among the Tatars as the person who killed their relative (called Temüjin Uge) in a battle eight years earlier.
[5] Yesügei and Hoelun had four sons Temüjin, (later known as Genghis Khan), Hasar, Hachiun, Temüge and a daughter, Temülen.
The Secret History of the Mongols records that in his youth Temüjin killed his brother Behter in a fight for food.