Good morning. I would like to discuss the granularity of surnames.

Spanish citizens have "surname1" (one of the parents, usually the father's surname) and "surname2" (usually another parent which is usually the mother's maiden name, although the surnames can be reversed by agreement of both parents).

There may also be other cases: a single mother, parents are two women or parents are two men. It should be noted that in Spain birth surnames never change except in the case of adoption of children or prior approval of a judge (in Spain women do not change or "lose" their birth surnames after marriage). The two surnames serve in Spain, therefore, for traceability: to disambiguate two citizens with the same first surname, to identify the second parent of a child even if the parents are not married, to identify the surnames of the maternal grandparents in case of a citizen being the son of a single mother.

As an example, a person can have a first surname "De La Fuente" and a second surname "Del Campo": this person does not have 5 surnames "De La Fuente Del Campo" in the "familyName" or in the " nameAndFamilyNameAtBirth"; If the second surname is not clearly differentiated from the first surname, it is sometimes impossible to infer which is the second surname of a Spanish citizen.

Granularity is important in my opinion and the problem is the current model is not valid for Spanish citizens, because in Spain there are two separate surnames, not just one, and I cannot correctly use "familyName" in the current model to differentiate both surnames for the parents traceability, so my proposal is not removing granularity but adding a differentiated "secondFamilyName" for some jurisdictions (more generic than the HL7 "mothersMaidenName" extension, see https://www.hl7.org/fhir/extension-patient-mothersmaidenname.html for reference).

Best regards,

Fernando.