Everybody on Earth is related by virtue of the fact that we’re all the distant grandchildren of the very first humans. Exactly when these grandparents were alive is up for discussion, but scientists think it was probably somewhere between 550,000 and 750,000 years ago. The first humans had children and they became brothers and sisters, who made way for aunts, uncles, nieces, nephews and, most confusingly, cousins.
The word “cousin” is often used loosely across cultures, and even throughout American history.
Source: First, Second, Third, Removed, Kissing — It’s Complicated! A Cousins Tutorial
