1
general::
Two or more things that are closely akin or very similar. For example, They may be made by different manufacturers, but these two cars are kissing cousins. This metaphoric term alludes to a distant relative who is well known enough to be greeted with a kiss. [c. 1930]
American Heritage Idioms
2
general::
Phrase(s): kissing cousins
relatives who know one another well enough to kiss when they meet. • Joe and I are kissing cousins, though we ain’t seen one another since we was kids. • Technically, we’re second cousins once removed, but I just say we’re kissing cousins.
McGrawhill's American Idioms And Phrasal Verbs