Antonio Romo and Juana Olivo

I am a descendant of Antonio Romo and Juana Olivo who married abt 1870 in San Luis Potosi. I have heard an old family rumor that they ran away together to marry. I have not been able to find the parents of either of these two. As far as I know they only had one child, Claudio Olivo Romo abt 1874 in Corpus Christi. Can anyone point me in the right direction to continue my research? Lynnda Lee Romo