The best way to describe Indian "uncles" and "aunties" is that they are collective nouns for anyone above your own generation who are not your parents or ancest

The best way to describe Indian "uncles" and "aunties" is that they are collective nouns for anyone above your own generation who are not your parents or ancestors. They could be related to your parents or friends of your parents or a random person on the street who is older. Kids literally walk into mom-and-pop shops and address the shopkeeper as uncle or aunty.