family line vs blood line

family line and blood line both are nouns.

Word	Noun	Adjective	Verb	Adverb
family line	Yes	No	No	No
blood line	Yes	No	No	No

As nouns, blood line is a hypernym of family line; that is, blood line is a word with a broader meaning than family line:

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

family line (noun)	blood line (noun)
people descended from a common ancestor	the hereditary derivation of an individual