His father was Marcos de las Casas, and his mother was Gertrudis de la Vega.
He married Gertrudis de Montemayor, daughter of Diego Rodriguez de Montemayor and Maria Ines de la Garza Gonzalez Hidalgo on 26 Sep 1679 in Monterrey.
He married Luisa Fernandez, daughter of Gregorio Fernandez de Tijerina and Maria Gonzalez. It was his second marriage. His wife died on 30 Sep 1692 in Monterrey. She was 16 years old.