Filipino Wanting Spanish Citizenship

[Miguel]

Hello,
I am from the Philippines and I want to apply for Spanish Citizenship. My great grandparents on grandmother's side are PENINSULARES and my grandmother (born 1890) is INSULARES. My great grandparents and grandfather (born 1885) are pure spaniards born and raised in Spain. They have not renounced their Spanish Citizenship. Their son, my father (born 1920) was born here in Manila. He never acquired Philippine Passport. I am in my 40's now and all of them are deceased. What are my chances of getting Spanish Citizenship by Origin? Thank You.