He was born circa 1757. His father was Juan Antonio Leal, and his mother was Antonia Garcia. His father owned Mier 55 grant, Starr County.
In 1782, he lived in Mier in household number 61. The church census recorded that he was single, español, and 25 years old. His household included 4 people:
Juan Antonio Leal, married, español, age 59.
Antonia Garcia, married, española, age 57.
Juan Jose Leal, single, español, age 25.
Jose Patricio Leal, single, español, age 22.