I'm having a problem understanding your writing, but it seems pretty simple to me. Are you Hispanic and thus, have at least 4 names? As in Pablo Rodrigo Santos Fernandez, with Santos being your mother's maiden name and Fernandez your fathers name? If that's the case, for you passport, keep it simple and just use your first and father's name - which is your surname, as usual.

As for your middle name, that would be Rodrigo.