family tree vs kin group

family tree and kin group both are nouns.

Word	Noun	Adjective	Verb	Adverb
family tree	Yes	No	No	No
kin group	Yes	No	No	No

As nouns, kin group is a hypernym of family tree; that is, kin group is a word with a broader meaning than family tree:

Other hypernyms of family tree include clan, kin, kindred, kinship group, tribe.

family tree (noun)	kin group (noun)
successive generations of kin	group of people related by blood or marriage