Mu'izz ad-Din Muhammad was born in 1149 in the Ghor region, which is now Afghanistan. The exact date of his birth is unknown. His father, Baha al-Din Sam I, was the local ruler of the Ghor region at that time. Mu'izz also had an elder brother named Ghiyath al-Din Muhammad. During their early life, Mu'izz and Ghiyath were imprisoned by their uncle Ala al-Din Husayn, but were later released by their uncle's son Sayf al-Din Muhammad. When Sayf died in 1163, the Ghurid nobles supported Ghiyath as their leader, and helped him to took over the throne. Ghiyath shortly gave Mu'izz control over Istiyan and Kajuran. However, the throne was challenged by many Ghurid chiefs during which Mu'izz helped his brother Ghiyath in defeating and killing a rival Ghurid chief named Abu'l Abbas.