sib vs blood relative

sib and blood relative both are nouns.

Word	Noun	Adjective	Verb	Adverb
sib	Yes	No	No	No
blood relative	Yes	No	No	No

As nouns, sib and blood relative are synonyms defined as:

sib and blood relative: one related by blood or origin; especially on sharing an ancestor with another

Other synonyms of sib include blood relation, cognate.

sib (noun)	blood relative (noun)
one related by blood or origin; especially on sharing an ancestor with another	one related by blood or origin; especially on sharing an ancestor with another
a person's brother or sister