Who are blood relatives?

No idea in reference to which context this query before us but doing complete justice to a query one could reasonably quote what Hon’ble Apex Court in a S. 498a IPC said ref. : U. Suvetha Vs. State By Insp. of Police & Anr. [https://www.indiankanoon.org/doc/953117/]   

Held: The word `relative’ brings within its purview a status which must be conferred either by blood or marriage or adoption. In the absence of any statutory definition, the term `relative’ must be assigned a meaning as is commonly understood. Ordinarily it would include father, mother, husband or wife, son, daughter, brother, sister, nephew or niece, grandson or grand-daughter of an individual or the spouse of any person.