My kids call my mom Gramma, but their father's mother is Puerto Rican so they call her Abuela. It's funny cause all her grandkids started out calling her Abuela, but as they grew the "American" in them caused them to start calling her Grandma, so of all her grandkids (I think she's up to like 11 now), only my two still call her Abuela. I told them to continue calling her that because it means a lot to her. Sure, they slip occasionally and call her Grandma, but not that often. And when they talk about her it's always said as Abuela. I believe it reminds my kids of their heritage, even if they don't speak Spanish.
