He was the son of Alejandro Montes de Oca, a military officer killed in the Battle of Buena Vista in February 1847, and his wife Guadalupe Saucedo.
Francisco Montes war Sohn des Offiziers Alejandro Montes de Oca, gefallen im Februar 1847 in der Schlacht von Buena Vista, und dessen Gattin Guadalupe Saucedo.