Call me what you will. As long as it’s respectful and affectionate. Uncle and Aunt are terms taht are both of those things, and now and then I call an older person who is not my uncle or aunt those names.
As for my own uncles and aunts, first time I see them in a visit, I will use their title and first name. Subsequently, I will call them by their familiar name.
I’m almost sixty, when I was young every adult had to be addressed by a title. Cousin X, Coach Y, Mr. Z. Now it’s different.
When introducing a friend to my mother, I ask her how she would like to be introduced. Until 15 years ago, she would say, Mrs. R. Now she asks to be introduced by her first name. I do honor my mother’s request.
On the other hand, several friends’ parents have invited me to address them by their first name. That feels rather odd, since I have known them for decades as Mr. S.