Tweedledum And Tweedledee Meaning

(pejorative, idiomatic) A pair of people who spend a lot of time together, and look and act similarly.

Example:   The radicals said that Nixon and Humphrey were Tweedledum and Tweedledee.
2007, Stephen Booth, Blood on the Tongue: A Crime Novel
  Some officers were starting to call Edendale's two detective chief inspectors Tweedledum and Tweedledee, because they were rarely seen except when they were sitting alongside each other at the head of a briefing.
25 August 2010, Seumas Milne for The Guardian online, Ed is the only Miliband who offers a genuine alternative
  With their apparently identikit backgrounds and bland politicians' patter, the contest has sometimes seemed an incestuous choice between Tweedledum and Tweedledee. When even the promised fratricidal war between the Miliband brothers failed to take off, one newspaper cartoonist illustrated a caricature of the contestants with the caption: Who cares who wins?