family line vs dynasty

family line and dynasty both are nouns.

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

As nouns, dynasty is a hyponym of family line; that is, dynasty is a word with a more specific, narrower meaning than family line:

Other hyponyms of family line include people, homefolk, house, gens, name.

family line (noun)	dynasty (noun)
people descended from a common ancestor	a sequence of powerful leaders in the same family