When DD was growing up, my DM had passed away before she was born and MIL passed away when she was 12. She called her Granni. When she was pregnant, she asked is the baby could refer to me as Granni, not that I was old but because it made her think of my MIL. (her words. LOL)She now has two boys and they call her MIL Mimi and I am Mimi with the Papa. Kids will call you what they want and I LOVE anything they call me.