In Kerala, and perhaps other parts of India, “auntie” or “uncle” are terms of endearment among youth for anyone of “respectable” age.  No blood ties are necessary. In many Western cultures the OED definition tends to prevail, respectively, for these two terms:

A sister of one’s father or mother; also, an uncle’s wife (= aunt-in-law).

A brother of one’s father or mother; also, an aunt’s husband (= uncle-in-law).

And cousins?

In Kerala, while the term cousin is used to formally define a relationship with someone, it is not used as a term of endearment.  This is interesting, as cousin has a more malleable definition:

First, second cousin , etc.: expressing the relationship of persons descended the same number of steps in distinct lines from a common ancestor.

The children of brothers or sisters are first cousins to each other; the children of first cousins are second cousins to each other; and so on.

The term second cousin, is also loosely applied to the son or daughter of a first cousin, more exactly called a (first) cousin once removed.