It takes two to tango

Generated image of tango dancers
It takes two to tango means that two people are usually responsible for a situation, especially when there is an argument or problem.

The expression became widely known after a popular song called It Takes Two to Tango was released in 1952. The phrase uses the tango dance as an image, since the dance requires two partners working closely together.

They both blamed each other for the argument, but it takes two to tango.