Uses in Spain are different and people have TWO family names, the first being the father family name and the second the mother family name. Very handy when doing genealogical research but not something Ancestry deals with in a proper way.
Anyway, if you have ancestors or links to people in Spain remember that Spaniards have two family names. For example the son of George Loring (1771-1843) and Maria del Rosario Oyarzabal Herrera is George Henry Loring Oyarzabal (1822-1901). Loring like his father, Oyarzabal like his mother.
If you prefer to write only one family name it should be the first (Loring in this case).
You can take a look at my tree if you want to see their names as should be written (mistakes apart :-)

Enjoy

Arturo Shaw