it takes two to tango
Definition from Wiktionary, the free dictionary
- (idiomatic) Some things need the active cooperation of two parties; blame is to be laid on both parties in a conflict.
- I can't do it by myself, and neither can you – it takes two to tango.
- He started it! Well, it takes two to tango.
some things need the active cooperation of two parties
Related terms 
- Gregory Y. Titelman, Random House Dictionary of Popular Proverbs and Sayings, 1996, ISBN 0-679-44554-4, p. 174.