folk vs blood line

folk and blood line both are nouns.

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

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

folk (noun)	blood line (noun)
the traditional and typically anonymous music that is an expression of the life of people in a community	the hereditary derivation of an individual
people in general (often used in the plural)
a social division of (usually preliterate) people
people descended from a common ancestor