Spanish people include the names of both the father and mother respectively. In white people society, a person named Sr Julio Diaz-De Los Santos would be referred to as a Mr Julio Diaz.
The reasoning for the long name is because Spanish culture sees marriage as a union of two families rather than the woman becoming a part of the man's family (and abandoning her birth family identity). Unfortunately, two surnames pisses off computer systems programmed by single surnamed-white people and are therefore not used in non native countries. Silly Latinx.