Our son married the most wonderful woman ever, but since she was almost 40 when we met her, and her parents are still alive, she calls us by our first names. I think that age has something to do with it...she's not 18 or 21, but an established businesswoman. When she told us we were going to be grandparents, she asked us right away what we'd like to be called. (Mimi and Papa). I don't really care what she calls us (although I think Mom would be nice) because every time we part she hugs us and says "I love you!" That's what really counts!