His mother, María Ramona Carrillo de Pacheco, was a sister-in-law of General Mariano Guadalupe Vallejo and a daughter of María Ygnacia López de Carrillo, the grantee of Rancho Cabeza de Santa Rosa. After the death of his father, Romualdo's mother married Captain John D. Wilson, a Scotsman, who sent Pacheco to Honolulu, Hawaii, for his education.
