I've never understood the whole calling someone aunty or uncle when they aren't, but maybe that's just because I didn't grow up with that. My parents had close friends, and I always just referred to them by name.
Like, if your kids refer to your friend as aunty, do you refer to her as your sister? I have one friend whom I think of more as a sister than a friend, but even then her kids just think of me by name.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker