I don't have any living grandparents anymore and my mom's parents had both passed by the time I was born. I called my dad's mom "nana." My dad's dad abandoned his family and I only met him once or twice...never called him anything. And I know it's a little weird, but my older brother has a different dad than me and his dad's mom always treated us all like we were her flesh and blood. I called her "granny."
Nana and Tata my Tata raised me hes has been the only dad I have ever had my real dad came into the pic when my son was in diapers that was 7 years ago