People with similar interests or characters naturally gravitate toward one another; like attracts like; birds of a feather flock together

To share the same interests, purpose, or ideals; to be like-minded

Literally meaning that similar sounds resonate together and similar smells attract each other; used to describe how people with similar interests or characters are naturally drawn to one another, gravitate together, and support each other.

evil people helping each other and working together to commit crimes