Hello Zara,

You need to prove not only that he was born in Spain, but that he never lost his Spanish citizenship.

I understand you do not live in Spain an d therefore the first thing to do is to make an enquiry at the Spanish embassy and then apply for a birth certificate for your grand grandfather. If the Spanish ancestry line was never interrupted, you could be considered a Spanish citizen by origins, but your grandfather and father must be recognized as Spanish citizens first.

In the event you can only prove that your grandfather was a Spanish citizen, but not your father, you can apply for the Spanish nationality after one year of legal residency in Spain.