Do you call them by their first names? Or do you call them mom and dad? Or something else? Also where are you from?

I am American and I call my husbands parents mom and dad and my husband calls my parents mom and dad.

Recently my sister married a German man and at her wedding her new mother in law embraced her and said, “I’m so happy to have another daughter!” My sister then said to her, “is it ok if I call you mom?” Because to be honest up until that point my sister hadn’t called her anything cause she wasn’t really sure how to address her. 😂 (she lives in Germany so they didn’t see each other often) she immediately said, “No. your children will call me Grandma but you can call me “first name.”

My sister isn’t that hurt about it. I think it actually offended me more 😂 but it got me wondering about different cultures.

I do find it odd that she called her a daughter and then said no to being called mom.

Any thoughts?