Portugal - Passport & Nationality - Portuguese Citizenship by Descent
the Portuguese parent was residing abroad at the service of the Portuguese State at the time of birth; OR
his/her birth is registered with the Portuguese Civil Registry; OR
he/she (or his/her legal guardian) declares that he/she wants to adopt the Portuguese nationality.
Portuguese nationality may also be acquired by an individual born outside of Portugal to (i) a Portuguese mother or father OR (ii) a mother or father born in Portugal in the following case:
Minors or incapacitated individuals whose father or mother had acquired Portuguese nationality, pursuant to a statement by his/her legal guardian declaring that the ward wants to adopt the Portuguese nationality.