Degree of consanguinity

Let's imagine that you have a cousin, and your cousin has a brother. The relationship between you and your cousin is pretty close, right? You might even consider each other to be best friends. But what about the relationship between you and your cousin's brother? Well, that's a little bit more distant. Sure, you might see each other at family gatherings, but you probably don't spend a lot of one-on-one time together.

Scientists and lawyers have come up with a way to measure how close or distant relationships are between family members. They call it the "degree of consanguinity." Basically, this just means how closely related two people are.

Let's use the example of your cousin and their brother again. You and your cousin share a set of grandparents, right? Well, your cousin's brother also shares those same grandparents with you. So that means your degree of consanguinity with your cousin's brother is 2. This is because you and your cousin's brother are both 2 generations away from your shared grandparents.

But what about other family members? Your degree of consanguinity with your own brother or sister would be 1, because you and your sibling share parents. Your degree of consanguinity with your aunt or uncle would be 3, because they are 2 generations away from your shared grandparents (just like your cousin's brother), but they are also one generation away from your parents (who are the children of your grandparents).

Why is this important? Well, in some countries and cultures, there are laws about who can marry whom. For example, in some places, it is illegal for cousins to marry because they are considered too closely related (their degree of consanguinity is 2). By measuring the degree of consanguinity between different family members, scientists and lawyers can help decide if certain relationships are appropriate or legal.