band together

bang some heads together

Attempt to get results from a previously ineffectual or argumentative group, typically by coercion or force.

birds of a feather flock together

People of similar character, background or taste tend to congregate or associate with one another; it is easier to establish friendships with people that one has a lot in common with.

bring together

To cause people to do something together; to bring about togetherness.

get one's act together

To become serious, organized, worthwhile, etc.

get one's shit together

To organize oneself in order to be able to deal with or achieve something; to mature.

get oneself together

Alternative form of pull oneself together.

get the band back together

To reunite a group of people or other entities.

get together

To start dating; to start being a couple.