Hello Catherine, I descend from the Martin Saenz branch and also had a difficult time looking for info on Marcelino and Margarita. I have assisted the author Joel Rene Escobar Saenz in his soon to be printed book about the Saenz family from 1500's - 1800's of N.L. and no info on the couple has been found (yet) in all the church records of Nuevo Leon. The accepted theory is that from Rodolfo Gonzalez Garza's book "Raices Hispanas" in which he states that Marcelino's parents were Miguel saenz benavides and Margarita Hinojosa. Good luck and let me know if u find anything new!