The phrase "blood relative" derives from the notion that the bond between family members is strong because they share the same bloodline. However, there are several synonyms for this phrase that are worth exploring. First, there's "kin," which refers to one's relatives or family. Next, "flesh and blood" is commonly used to describe family connections, emphasizing the physical tie between them. Another synonym is "lineage," which pertains to the direct descent from a common ancestor. Lastly, "relation" or "family member" are straightforward ways to describe someone's familial connection. Ultimately, the use of these synonyms highlights the importance of family ties and the various ways they can be expressed.