sib vs blood relation

sib and blood relation both are nouns.

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

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

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

Other synonyms of sib include blood relative, cognate.

sib (noun)	blood relation (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