Little Background Context for Sibling Relationship

I noted on another thread the lack of historical context regarding the film's main plot. Similarly, there is no backgrounding whatsoever to the brothers' relationship. Terry seems to constantly be looking out for and deeply concerned about his younger brother Matt, who returns the favour, by sticking a gun in Terry's face and threatening him throughout the film. We can see what director Dearden wants us to get, but that doesn't mean it makes a lot of sense.🐭