Thank you for the info Athol. I understand that Miguel de Montemayor was the grandson of Don Diego de Montemayor and Juana de la Cerda.
I have a question for you. I am looking for the marriage of Maria Eufemia Montemayor and Jose Dionicio Martinez. Maria Eufemia was daugther of Diego de Montemayor y Maria Lucia de la Garza. I don't have the parents of Dionicio, but I think they were Andres Martinez and Lugarda de Benavides, but I am not sure.
Manuel Ambrosio Joseph b. Dec 10, 1750 was the oldest son of Maria Eufemia and Jose Dionicio, so they got married probably 1748-1749.