No - I always used the names their kids did; Muvver and Popsi.
I call ‘em by their first names. I’m actually about as close to my in-laws’ age as to my wife’s, so I don’t feel a generational gap between us.
In Israel we call everyone by their first name (or nickname, if they prefer). Old people, young people, teachers, bosses, commanding officers…
The only problem with my in-laws is that we named my son after my FiL, which can cause some confusion at times. When they’re together, we call them “Big [Firstname]” and “Little [Firstname]”, which my FiL loves and my son isn’t crazy about. Also, my FiL already had a cousin with the same name who went by "Little [Firstname] at family gatherings; we promoted him to “Medium [Firstname]”.
First names, and I don’t think I’d have entertained the idea that I’d call them anything different for more than a minute or two- I’m not subservient to them in any way; I only expect them to treat me as a peer, as I married their daughter when I was 35, so none of this “we rule the roost” bullshit.
If they wanted me to call them Mr and Mrs In-Laws, I’d fully expect to be called Mr. Bump as well.
First names. It took a bit of doing, as I’d known my in-laws and my wife for over a decade before we started dating. My mother-in-law was even my Odyssey of the Mind coach. So moving from the Mrs. designation to her first name was jarring for the first year or so.
First names, though I call my mother-in-law “Ma” on occasion (to distinguish her from my own mother, Mum.)
I solved the problem before it started…I married an orphan. No in-laws. 
My husband always called my mother “Mrs. ___” because she was a stickler for such things and wouldn’t have been amused if he hadn’t. They got along very well, though, she thought the world of him and vice versa.
My DIL calls me by my first name, which is fine. It feels right because I’ve known her for such a long time (they dated 5 years before they got married and were members of the same group of friends prior to that). Plus, this is a much more casual era than it was 35 years ago when I got married.
I call my FiL either Pop or his first name. As I’ve gotten older, it’s usually his first name. But I’ve always called my step-MiL by her first name. (My MiL passed away before Hubby and I married.)
Hubby goes to great lengths to avoid addressing my father by name, but when he can’t avoid it, he calls my dad by his first name.
I had a friend who’s father died while he was in Jr High. After a year or so passed, his mother married a widower with 2 daughters. Older of the daughters was, let’s be kind, problematic and not shy about bending the truth completely out of recognition if it suited her purposes.
I’ll skip the details.
Once stuff had settled down, my friend referred his mother’s second husband as “My Mother’s Second Husband” and usually addressed him as “Sir”, though occasionally as “Mr. Lastname.” “Dad” or “Father” was definitely OUT of the question as “My father/dad is dead. Mr. Lastname is my mother’s second husband.”
Well, I’ll be damned. I actually can’t remember what we did, it’s been so long since any parents were still alive.
I don’t call them by any names. When speaking of them, I refer to them as “Your Dad” or “Your Grandfather” or “Her Dad” or "The kid’s grandparents.’
When my husband and I got engaged, I asked him what he thought I should call his parents. He just went ahead and asked them: “What do you want Sigmagirl to call you?” They said “Why, George and Martha, of course!” I was relieved because my parents were long gone, and I really didn’t want to call other people Mom and Dad.
I generally manage to work around it so I don’t have to. I only use their first names when I absolutely cannot avoid it.
I call my wife’s parents “Mrs S.”* and “Dr S.”, and my wife calls my parents Mom & Dad. That’s just the way the dynamics of the relationships go. I do sometimes refer to my in-laws by their first names when referencing them to each other (“Mrs S., when did BillyJimBob want me to come install that new router?”), but never as a direct address.
- Yes, before Orphan Black made this cool
My parents insisted that my wife call them by their first names, since “Mom and Dad” is archaic, formal and stuffy. And my in-laws insisted that I call them “Mom and Dad”. Which did not surprise me, since they are archaic, formal and stuffy.
I hate it. I have a mother and a father, and I have a hell of a lot more respect for them than I do for my in-laws, and to use the same term for both sets of parents is disrespectful to my actual parents. I only continue to do it out of respect for my wife, but I avoid calling them anything whenever possible.
I avoided calling my wife’s parents and step-parents (one of each) by anything at all. There was really nothing I felt comfortable with. My kids call me Pops and my wife Moom (that started as a typo in an email, she answered in kind and they all picked it up). My two daughters-in-law use those names but my son-in-law calls us by our first names. At first, I was slightly disconcerted, but I’ve gotten used to it.
No in-laws of my own, but my SIL called my parents Mom and Dad. It used to bother me until I found out how abusive her family of origin was. The most touching moment of my mother’s memorial service was when SIL said, “Inez didn’t give birth to me, but she gave me life.”
I call my late wife’s parents Mom and Dad, and I call my current wife’s parents by their first names.
Yep, first names. Both my parents were alive so it would have been weird to call the Mom and Dad.
First names now. After we got married my FIL never said what to call him, so I didn’t call him anything for a year or so. Mr. didn’t seem right after the wedding.
He was pissy about it, but never spoke up. Never liked/like talking to him anyway.