Your result
Portugal — Reacquiring Lost Citizenship
Possible
The declaration belongs to them, and if they make it, your position changes with it.
Anyone who lost Portuguese nationality before 3 October 1981 by voluntarily acquiring another one can reacquire it by declaration. There is no opposition procedure, no language requirement and no residence requirement — and the reacquisition is backdated to the date the foreign nationality was acquired.
That backdating is what reaches you. If your parent reacquires, they are treated as having been Portuguese when you were born, which makes you the child of a Portuguese parent — a registration with no test and no residence requirement, at any age. If it is a grandparent, their reacquisition restores the line, and your claim is the grandchild claim, which since 19 May 2026 carries language and integration tests.
So the first question is whether that person is alive and willing. If they are, their declaration is the fastest and cheapest step available to your whole family, and it is worth explaining to them that it costs them nothing: Portugal does not require anyone to give up the nationality they took.
If they have died, the position is more complicated and depends on whether the loss was ever registered. That is a question to take advice on with the documents in hand rather than to guess at.