In Spain there are two last names, not a last name "with a space" between words. Traditionally paternal first, maternal second, although the law has changed to be able to use any order. Both must be present in legal documents or ID card, passport, etc.
It is a real pain for Spaniards living abroad. It is not a middle name, a two worded last name, or anything of that sort. Full legal name = First name + Parent A's 1st last name + Parent B's 1st last name.
Edit : As pointed out in another comment, a Spanish last name can be a two worded one, and a first name can be as well, and often is. So you could end up with for instance, a 5-word nightmarish José Carlos ( 1st name ) García ( 1st last name ) De Maestre ( 2nd last name ).
It is a real pain for Spaniards living abroad. It is not a middle name, a two worded last name, or anything of that sort. Full legal name = First name + Parent A's 1st last name + Parent B's 1st last name.
Edit : As pointed out in another comment, a Spanish last name can be a two worded one, and a first name can be as well, and often is. So you could end up with for instance, a 5-word nightmarish José Carlos ( 1st name ) García ( 1st last name ) De Maestre ( 2nd last name ).