I've only recently found those same names in my family tree. If you're no longer interested maybe someone else is.
From what I've read, back then children (or maybe their parents) had a choice as to which surnames in their family they used, so you will find children with the same parents with different last names. Also, the fact that in Mexico at least people use both paternal and maternal surnames makes it very difficult to search for ones' ancestors, in particular when the people cataloguing the data are not familiar with these customs and so searches on familysearch.org are very difficult to do.
I've noticed that whenever one ancestor was prominent (or famous), that last name would often be given to the descendants. For example, Sanchez and Navarro became Sanchez-Navarro. This probably also has to do with the fact that Sanchez is a very common surname, so in order to distingush tehmselves from other lines, the Sanchez and Navarro clan became Sanchez-Navarro.
There is probably more factual information online but I haven't found it.
By the way, I am also a descendant of Domingo de la Fuente, so if you are still doing research please contact me so we can share information. email@example.com