Noun

1. People having similar characters, backgrounds, interests, or beliefs.
   • c1710, Jonathan Swift, "A Conference," lines 11-12,

     And since we're so near, like birds of a feather,

     Let's e'en, as they say, set our horses together.

   • 1876, Anthony Trollope, The Prime Minister, ch. 51,

     Birds of a feather do fall out sometimes.

   • 1951, "As Bad or Worse?," Time, 21 May,

     Paul Blanshard has two bogeymen of almost equal fearsomeness: one dwells in the Kremlin, the other in the Vatican.... Blanshard has satisfied himself that Stalin and the Pope are pretty much birds of a feather.