There isn't a lot of evidence about this outside of the bible itself. There are a bunch of instances of people knowing and spending time with their cousins or uncles, covering pretty much the entire bible from Abraham and his nephew Lot to Mordechai and Esther (written much later in the Persian period) and these texts don't remark on the fact that they're close, so it probably wasn't very unusual.

In addition, the sexual prohibitions in Leviticus 18 list aunts and uncles (but not cousins) in the same list as parents, siblings, etc, so at least that author seems to have thought of them as close relatives.