Answer
One parent can act without the other only if there is proper consent, a power of attorney, or a document confirming sole authority. For a minor, the involvement of both legal representatives is usually required when submitting the application, signing, or collecting the cédula.
If the other parent is abroad, notarized consent should be prepared in advance with a precise description of the action: applying for residency, obtaining an ID card, signing documents, or other powers. A foreign document may require an apostille and translation.
If the other parent has died, has been deprived of parental rights, is unknown, or there is a court order on guardianship, the relevant document or court decision must be prepared. A standard letter, a scan of a signature, or a verbal explanation does not replace documentary proof of authority.