I call my FIL by his first name, at his insistance. And my hubby does the same for my rents. But now that my parents have grandkids… we all kind of just started calling them nanny and pop-pop. I think when I have a kid, whatever they call my FIL, that will probably stick.
One of the cultural artifacts of Southern Louisiana is an informal form of address for in-laws and family friends that are a generation ahead of the speaker: “Mister/Miss FirstName”. Yes, you use “Miss FirstName” even for married women.
This applies all life long. When I was a kid, my mom’s friends were Miss Dot, Miss Peggy, and so forth. Our neighbors were Miss Clara, Mister Billy, Miss Pat, etc. 30+ years later, I still address all these same people the same way.
My dad has always called his own friends “Mister FirstName” when speaking about them referentially. I think this is the same usage extended a little further.
I think an interesting point for me is what do you call your SO’s parents - because some of us are long termers without the wedding march - and that’s where it can get interesting.
Gonna start a thread on it - I think. . . .
I believe it should be based upon how they introduce themselves to you. If they prefer to be called Mr. Lastname or Mrs. Lastname, that’s their preference. Although, under my breath I would say they have a stick stuck up their ass to expect such formality from their child’s spouse.
The exception to this rule, IMHO, is when they request that you call them mom/dad or mother/father. In that case I believe it is up to the son/daughter in law to chose to be that intimate in their address. As already mentioned, I have parents, and I may not feel comfortable addressing you in such an intimate manner.
I’m 31 and call my in-laws by their first names.
My MIL is in her 60s, and refers to her MIL (my FIL’s mother) as Mrs. Lastname
My wife calls my parents by their first names, and my grandparents as “Grandma/Grandpa Firstname.”
My husband calls his father by his first name more often than not, so I do too! Since his mother passed away long before I met the family, I don’t really have a MIL, but my FIL’s partner has more or less filled that role and gets addressed by her first name, too. Same with his grandparents, though my own grandparents are/were usually called Grandmaman/Grandpapa.
First names. They are not my parents, and I’m not a child (no Mr./Mrs. Lastname).
First names, or “Grandma” and “Grandpa” if my daughter is around.