Just as, I imagine, in Italian, many last names and names have articles and prepositions in them (de, los, del, de los, de la, de las, la, etcetera); these should NEVER be capitalized, and must be ignored for sorting, both of which are invariably done wrong.

And there are some names that can also be, less frequently, surnames (Santiago, Esteban, Miguel, for example).

And we do legally have two last names, one from the father, one from the mother, but we often only quote the first one, for brevity.

For traditional reasons, in the vast majority of cases, you get the first last name from your father, but nowadays parents have that choice too.

I would not be surprised if you could pass on your SECOND last name, instead of the first one, offering a full four possibilities for naming your progeny, although I know of no such cases. I do *believe* that all brothers have to have the same set and in the same order, but Spanish law is so permissive with that sort of dumb liberties that I could easily be wrong.

So there is no safe way to split “José Miguel de la Rosa” without more information. Most likely the name would be “José Miguel” and there would only be one last name quoted, but it could also be that the name were “José” and the last names “Miguel” and “de la Rosa”. So for Spanish name splitting, some complicated heuristics are necessary improve certainty, and still they will fail sometimes.

My own name, for example, has as last name Ruigrok van der Werven, but if you would take the general Dutch rule that last names have a ‘van ‘ part, you might think van der Werven is my last name and Ruigrok is part of my first or middle name. And ‘van’ is not considered part of the last name and is registered as a prefix and this system does not provide for that specific part.