blood line vs line of descent

blood line and line of descent both are nouns.

Word	Noun	Adjective	Verb	Adverb
blood line	Yes	No	No	No
line of descent	Yes	No	No	No

As nouns, blood line and line of descent are synonyms defined as:

blood line and line of descent: the hereditary derivation of an individual

Other synonyms of blood line include ancestry, blood, bloodline, descent, line, lineage, origin, parentage, pedigree, stemma, stock.

blood line (noun)	line of descent (noun)
the hereditary derivation of an individual	the hereditary derivation of an individual
	the kinship relation between an individual and the individual's progenitors