At fifteen, Temüjin (Genghiz) married Börte, with Dei Sechen, her father, warmly welcoming him and presenting the couple with gifts, including an expensive sable cloak for Hö'elün. Seeking support, Temüjin allied with Toghrul, khan of the Kerait tribe, by gifting him the sable cloak, securing his protection and beginning to build his own following, with figures like Jelme joining his ranks. During this period, Temüjin and Börte welcomed their first child, a daughter named Qojin.

In retaliation for Yesügei's earlier abduction of Hö'elün, around 300 Merkits attacked Temüjin's camp, abducting Börte and Sochigel. Börte was forced into marriage according to levirate law. Temüjin sought help from Toghrul and his blood brother Jamukha, now a tribal chief, who assembled an army of 20,000 warriors. They successfully rescued Börte, who was pregnant and later gave birth to Jochi, whose paternity was questioned but was raised by Temüjin as his own. Over the following years, Temüjin and Börte had three more sons—Chagatai, Ögedei, and Tolui—and four daughters, underlining the family's growing prominence.