Temüjin is born on the steppes (grasslands) of what is now Mongolia. He is the son of Yesügei, a member of the royal Borjigin clan of the nomadic Mongol people."

Temüjin grew up with three brothers, Qasar, Hachiun, and Temüge, one sister, Temülen, and two half-brothers, Behter and Belgutei. As common to nomads in Mongolia, Temüjin's early life was difficult.

At age nine, his father arranged a marriage for him and delivered him to the family of his future wife Börte of the tribe Khongirad. Temüjin was to live there serving the head of the household Dai Setsen until the marriageable age of 12. While heading home, his father ran into the neighboring Tatars, who had long been Mongol enemies, and they offered his father food under the guise of hospitality, but which instead poisoned him. Upon learning this, Temüjin returned home to claim his father's position as chief, but the tribe refused him and abandoned the family, leaving it without protection.

For the next several years, the family lived in poverty, surviving mostly on wild fruits, ox carcasses, marmots, and other small game killed by Temüjin and his brothers. During this time, Temüjin's mother, Hoelun, taught him about Mongol politics, including the lack of unity between the different and the need for arranged marriages to solidify temporary alliances, and strong alliances to ultimately ensure the stability of Mongolia. Over time, Temüjin's older half-brother Behter began to exercise power as the eldest male in the family, creating tension in the family that boiled over during one hunting excursion by the men of the family and resulted in the death of Behter at the hands of Temüjin and his brother Qasar.