1Similarity, especially in appearance, between members of the same family or family line; an instance of this.
2Similarity between things which are considered to be connected or related; an instance of this.
3Chiefly in or with reference to the writings of Ludwig Wittgenstein: one of a network of overlapping but discontinuous similarities between extensions of a concept or meanings of a word. Frequently attributive, as "family resemblance concept", "family resemblance term", etc.
family resemblance/ˌfam(ɪ)li rɪˈzɛmbl(ə)ns/ /ˌfam(ə)li rɪˈzɛmbl(ə)ns/
Mid 18th century; earliest use found in The Critical Review. From family + resemblance.