From IMDB:

A depressed uncle is asked to take care of his teenage nephew after the boy’s father dies.

Such a sad film from beginning to end.  Just be prepared to get involved in a story that almost certainly cannot have a happy ending. For two hours you will see an emotionally numb Lee Chandler (played well enough by Casey Affleck) trying as best he can to find a solution for his nephew whose father (Lee’s brother) has just died. That problem is made more difficult by the all-around family dysfunction in which marriages have failed such that wives and mothers have moved away from their families.  Patrick, the nephew, is a normal adolescent seemingly more interested in getting laid by his multiple girl friends than in the death of his father. In this regard Lee is very permissive.  In general the relation between Lee and Patrick are begrudgingly positive.

Only when Lee gets drunk and boils over in a bar is there any violence in the film.

See also the Wikipedia article.

For some reason, it was not until the very end of the film that I realized that Lee is clinically depressed (for very legitimate reasons). Forgive my point of view, but couldn’t anyone have stepped in and suggested that Lee get professional help in this regard? But then that would spoil the story.