A more thorough explanation:

Definition: Cognatic (kog-nat-ik) is an adjective used to describe a relationship that exists between cognates. Cognates are people who are related to each other through a common ancestor, either through the mother's or father's side of the family.

Examples:

• My cousin on my mother's side is also my cognate because we share the same maternal grandmother.
• My uncle on my father's side is not my cognate because we do not share a common ancestor through my father's side of the family.

The examples illustrate how cognatic relationships work. In the first example, the speaker and their cousin share a common ancestor through their mother's side of the family, making them cognates. In the second example, the speaker's uncle is not their cognate because they do not share a common ancestor through their father's side of the family.