A more thorough explanation:

Consanguineus is a historical term that means a person who is related to another person by blood. This means that they share a common ancestor, like a grandparent or great-grandparent.

• John and Mary are consanguineous relatives because they are first cousins. Their parents are siblings, so they share a common set of grandparents.
• When researching family history, it is important to look for consanguineous relationships to understand how people are related.

The examples illustrate the definition of consanguineus by showing how people can be related by blood through a common ancestor. In the first example, John and Mary are consanguineous because they share a set of grandparents. In the second example, researching consanguineous relationships helps to understand family history.