1st met now DH's DP when I was much younger so called them Mr & Mrs [ ], expecting them to say call us by our 1st names. They didn't.
8 years and a lot of Mr & Mrs-ing later, DH and I got engaged. MIL announced that now I am family I could have the honour of calling her Elizabeth (obviously not real name). But, everybody else calls her Beth. Everybody from next door neighbours to the postman. I am the only person in the World expected to call her by her full name.
I really only questioned it when one of my friends who she'd met twice (but is an old Etonian - which she likes) called her Mrs [ ], and she responded call me Beth. Which he now does.
AIBU to think this is ridiculous?