be brothers/sisters under the skin

be (all) brothers/sisters under the skin

Of two or more people, to have thoughts or feelings in common, despite other obvious differences between them. As much as you dislike your chatty new co-worker, she's as nervous and insecure as you are—you're really sisters under the skin.
See also: brother, sister, skin
Farlex Dictionary of Idioms.

be (all) brothers/sisters under the ˈskin

be men/women with similar feelings, in spite of outside appearances, position, etc: Actors and politicians are brothers under the skin. They both need public approval.
See also: brother, sister, skin
Farlex Partner Idioms Dictionary
See also:
  • be (all) brothers/sisters under the skin
  • sister
  • read (one's) thoughts
  • at the back of (one's) mind
  • at the back of your mind
  • cut both ways
  • cut both/two ways
  • it cuts both ways
  • it cuts two ways
  • There is no accounting for taste