To be in an extremely close and interdependent relationship, like two inseparable entities.
他们从小一起长大，情同手足，彼此腹背相亲
They grew up together, like siblings, and are extremely close to each other.
Era:
Ancient
Frequency:
Next Idiom
To be in an extremely close and interdependent relationship, like two inseparable entities.
Era:
Ancient
Frequency: