Platonic uncles

My father had a single sister. My mother had brothers and sisters. I should ask, but I wonder if this lack of paternal family is why my father’s friends were my uncles. I cannot think of any friends my mother had who were platonic aunts or uncles.

I still honor these men with “Uncle” titles. Occasionally, if it becomes confusing, I will explain they’re a friend of Dad’s.

What led me down this thinking is I also have the single sibling. Maybe I should label my friends as uncles for Fleur? How does one go about this? Ask permission?