1 internal disunity dissolves at the threat of an invasion from outside (idiom)
兄弟阋墙
xiōng dì xì qiáng
1 internecine strife (idiom); fighting among oneself
吴下阿蒙
Wú xià ā Méng
1 General Lü Meng 呂蒙|吕蒙 of the southern state of Wu (idiom); model of self-improvement by diligent study (from unlettered soldier to top strategist of Wu)
亲兄弟，明算帐
qīn xiōng dì , míng suàn zhàng
1 even with your own brother, keep clear accounts (idiom)
阿谀奉承
ē yú fèng chéng
1 flattering and fawning (idiom)
2 sweet-talking
难兄难弟
nán xiōng nán dì
1 lit. hard to differentiate between elder and younger brother (idiom)