Jose Guillermo Rubio was born circa 1775, the son of Juan Rubio and Juana Bautista (Margarita) Mendez.
In 1782, he lived at Junta de los Rios. The church census recorded that he was a child, casta, and 7 years old. His household included 9 people:
Juan Rubio, casta, married, age 31.
Juana Bautista (Margarita) Mendez, casta, an unmarried girl, age 37.
Maria Trinidad Rubio, casta, an unmarried girl, age 18.
Maria Josefa Rubio, casta, an unmarried girl, age 17.
Jose Pio Rubio, casta, a child, age 13.
Jose Rafael Rubio, casta, a child, age 7.
Jose Guillermo Rubio, casta, a child, age 7.
Jose Maria de Jesus Rubio, casta, a young child, age 3.
Maria Tadea de la Cruz, india, single, age 61.