I am a South African citizen living in Cape Town, South Africa. My grandfather and great grandparents emigrated to South Africa from Madeira when my grandfather was just a baby. My grand father died before I was even born and my grandmother who is now also deceased only had his South African ID. I there any way I can find out whether my grandfather was registered or had a Portuguese passport before he came to South Africa as a child and how do I go about getting these documents.

If your father obtained dual citizenship through your grandfather, and he failed to meet minimum length of stay in Portuguese, as second generation outside the country, his citizenship would be automatically revoked.