The parents came, for the most part, from old hidalgo families long resident in Alcalá de Henares, although the patrilineal descent ultimately stemmed from the village of Cetina, in the Kingdom of Aragon.
The father, possibly owing to family influences, obtained in 1536 the job of almoxarife mayor (chief tax official and treasurer) for the city and its ports.
In 1539 Andrea del Castillo married Francisco de Montejo y León; the couple would eventually help found and settle the city of Mérida.
The following January the city of Mérida was founded, inscribed in the roster of first citizens (vecinos) appears the name of the aforementioned Beltrán de Zetina (sic).
María del Castillo (the third sibling so surnamed) married influential conquistador Francisco Tamayo de Pacheco and settled in Mérida.
[4] Gregorio de Cetina was for a time steward of the chapel of San Juan Bautista, in Mérida, position from which he profited financially.
The Cetinas were related by blood or marriage to the Montejos, the Pachecos, the Ortizes de San Pedro, the Rozas, among others, all of whom are counted as being among the first colonizers of Mexico and other lands.