family members or close friends should speak directly and avoid unnecessary politeness or formality with one another

咱们是多年老友了，一家人不说两家话，你就别跟我见外了。

people who are on the same side or from the same group should stand together and support one another

我们都是一个公司的同事，一家人不说两家话，有什么困难大家一起解决。