I know I'm late to the party, but since my daughter has six living grandparents and three living greats, and unique names for all I thought it would be worth a post.
My mother and stepfather are Grand-Chris and Grand-Kev (their names are Christine and Kevin, and both think they are too young to have "real" grandparent names, like Grannie or Grampa).
My father and stepmother are Grandpa and Nana (pretty traditional).
My M-I-L and F-I-L are Grandma and Poppa.
My (maternal) grandparents are Gramie and Grandfather (That is what my brother and I have always called them, yes even as little kids we were required to call him "Grandfather". It seems very Victorian, but that's what we did).
My wife's grandmother is Gamma Lily (her name is Lillian, and she is Gamma Lily to all of her grandkids and great-grandkids, of which there are literally dozens.
We like the unique names so we don't have to resort to the "Grampa [surname] or Grampa [surname]?" confusion.
