What term is used to refer to blood relatives or kin?

The term that refers to blood relatives or kin is "consanguinity." This word specifically denotes the biological relationship between individuals who share a common ancestor, indicating a direct blood relationship. In the context of family and kinship, consanguinity is crucial as it legally and culturally defines the connections that exist based on shared genetic lineage.

This term is often used in various discussions, such as legal contexts regarding succession, inheritance, and marriage restrictions, where understanding the degrees of blood relationship is important. The other options do not carry the same specific meaning related to blood relationships; for example, "affiliation" broadly refers to a connection or relationship but does not specify blood ties, while "connection" and "relation" could refer to many types of associations, not limited to those defined by blood.