同どう腹ふく

noun

born of the same mother; kindred spirits

Literally 'same belly', used for siblings from the same mother, and figuratively for people who share the same intentions or are in cahoots.

• 彼かれらは同どう腹ふくの兄きょう弟だいだ。

  They are brothers born of the same mother.

• あの二人ふたりは同どう腹ふくだ。

  Those two are kindred spirits (or in cahoots).