Will I qualify for Itallian Citizenship if my grandfather was Italian, but he never married my Grandmother?

Back in the Apartheid Regime in South Africa - A white man could not marry a black or Coloured woman, however, my grandfather lived with my grandmother as husband and wife for over 35 years and had 5 children with her, one of which is my mother - would I stand a chance of getting italian citizenship considering that my grandparents were never legally married?