Alamán's father immigrated from Navarre and accumulated a fortune in mining. His mother held the title of the fifth marchioness of San Clemente. Alamán's father was his mother's second husband after her first husband, Brigadier Gabriel de Arechederreta, died. Alamán had an older half-brother, Juan Bautista Arechederreta. A formative event in Alamán's life, which he wrote about in his autobiography, was his witnessing the sack of Guanajuato during the revolt by Miguel Hidalgo in 1810 where an Indian and mixed race mob captured the city granary ("alhondiga") and killed those taking refuge inside. This experience may have influenced his lifelong devotion to conservative politics and his nostalgia for monarchic rule for Mexico.