Now that is interesting. I'm 55. In my husband's family they called their grandparents by Grandpa Surname. Never a first name. Aunts and uncles were Aunt Jane or Uncle John. Adults were always Mr. Mrs. etc. In his family, InLaws were called Mom/Dad Surname.
In my family, We did the same except we called grandparents I guess depending on what they wanted. My dad's parents were Grandma/Grandpa Surname (but I never actually met them). I grew up around my mom's parents and they were Grandma Jane and Grandpa John (or 'first name' grandparents). In my family InLaws were called by their first name.
For our children, their grandparents were 'first name' grandparents. Their Great grandmother was a 'surname' grandparent. Our children's spouses call us by our first name. Our grandchildren call us grandpa/grandma surname (I hate it!) To me, to call a grandparent Grandma Jones is too formal and if the grandparent doesn't like it, not showing anyone respect.
My mom had one cousin who was almost as old as my grandmother. He was called Uncle Lloyd. Probably because my mother called him that. However, as long as I can remember, my brother called him plain Lloyd. However, my mother's other cousins were always just called by their first names.
In short - too late - we were raised to show respect by using titles. However - as others have stated, true respect is to call people what they want to be known as, whether it agrees with your family tradition or not.
I'm called Mary Ann by my nieces and nephews, friends, children's friends, etc. I don't need a title to feel special or respected. I feel that titles are something you use when you don't feel comfortable with a person. If someone used a title when talking to me, I'd wonder why they don't like me or feel comfy around me.
Mary Ann