My parents called their grandparents "Maa Jee/Miyan Jee". My parents called their parents "Aami jee/Abu Jee" and that is what I refer to my grandparents as. I call my parents "Aami/Abu". Now I see my nephew (brother's son) calling my parents Aami/Abu. However, my other nephew (sister's son) will, InshAllah, be saying Maa Jee and Miyaan Jee when he starts speaking fluently. It was either that or it would have been Nani jee/Nana jee.
My nephews call their parents Mama/Baba.
Its interesting how what we choose to address our parents changes every generation.
We called our nana "baba" which is what my mom and her siblings called him...my nani is "nani ammi" and my mom's elder sister "Khala Ammi".... I never saw my dada, but my dadi was "Amma" which is what everyone called her....
We also have the term "Ammanee" (not sure if I'm spelling it correctly!) which is what we called my Nana's sister...this term is used alot in Hyderabad for grandmothers/elder female relatives.
I called my parents Papa & Ammi, my husband also called his dad Papa...so that's what our boys call him