kissing cousin

plural kissing cousins

1. A relatively distant relative, or a friend, who is familiar enough to be greeted with a kiss.

   Synonyms: kissing kin

2. figurativelyA thing which is related or similar to another thing.

   Silicon is a “kissing cousin” of carbon. Notice it immediately below carbon in the Periodic Table. The arrangement of silicon’s outer electrons resembles those of carbon. For this reason, silicon and carbon are chemically similar.

   1994, Neil deGrasse Tyson, Universe Down to Earth, New York, N.Y.: Columbia University Press, →ISBN, page 175

   1 more example

   [A]fter the initial public brouhaha, wildlife administrators will suddenly decide that the classification of the Aleutian Canada goose as an endangered species was a gross mistake all along. Either the bird will be downgraded to "threatened" status—which means it can be hunted—or it will be declared a nonspecies, as has already happened to all its taxonomic kissing cousins.

   1981 September, George Reiger, “Conservation: What’s in a Name?”, in Field & Stream, volume LXXXVI, number 5, New York, N.Y.: CBS Publications, →ISSN, →OCLC, page 107, column 1

   Synonyms: cousin, cousin-german, kissing kin