Your post interested me because my grandmother was also named Isabel & was born in San Luis, Potosi. Her maiden name was Isabel Milan Zarazua. She married Jacobo Milan Santillan & their children were Anastasia, Basilio, Marcelino, Juan (my dad), Celia, Felix, Gumercindo, Lucia, Alejandro, and Doroteo Santillan. I think my grandfather Jacobo's father was named Margarito Milan Santillan. They later migrated to Ciudad Acuna in northern Mexico. I do know the roots of our family go back to San Luis, Potosi.