I hate when people (my DP included) expects my kids to call his boss or friends uncle. I always correct him and if they are just his friends they get called by their names if its his boss he gets Mr XYZ.
He tries to call my cousin Aunty for the kids but Im like NO she is my cousin, NOT their aunty.
For me, its a privalage to have a title. Someone close to the kids. Grandparents get one and great grandparents, aunty and uncle's, but anyone else is a name.