How old was Genghis Khan when his father arranged his first marriage?

Genghis Khan (born Temüjin, c. 1162 – August 18, 1227) was the founder and first Great Khan of the Mongol Empire, which became the largest contiguous empire in history after his death. He came to power by uniting many of the nomadic tribes of Northeast Asia. After founding the Empire and being proclaimed Genghis Khan, he launched the Mongol invasions that conquered most of Eurasia.

Campaigns initiated in his lifetime include those against the Qara Khitai, Caucasus, and Khwarazmian, Western Xia and Jin dynasties. These campaigns were often accompanied by large-scale massacres of the civilian populations – especially in the Khwarazmian and Western Xia controlled lands. By the end of his life, the Mongol Empire occupied a substantial portion of Central Asia and China.

Temüjin had three brothers Hasar, Hachiun, and Temüge, one sister Temülen, and two half-brothers Begter and Belgutei. Like many of the nomads of Mongolia, Temüjin's early life was difficult. His father arranged a marriage for him and delivered him at age nine 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.