If the aim of documentary film is to uncover a cosmos of human frailty in a grain of sand, then Joe Berlinger and Bruce Sinofsky topped out with Brother’s Keeper, their heartrending 1992 doc about a band of brothers whose lives are so primitive that they approach the feral. In 1990 rural New York, ailing dairy farmer William Ward is found dead in the bed that he shared with one of his three brothers for most of his life. When a D.A. comes calling, he finds the Wards living in unvarnished poverty, functionally illiterate, and largely untouched by modern mores. Soon prosecutors light on brother Delbert as the culprit of not only murder but incest, while the media creep in to paint the Wards as a fin-de-siècle freak show. Only when the local townsfolk rally to their aid do the brothers finally get what they needed—time and compassion—and, in the end, these are the gifts of the filmmakers, too. Berlinger and Sinofsky depict the Wards with such patience and thoughtful distance that, ultimately, it’s the moral authorities that dog the Wards who seem most barbaric, while the strange, rough men at the center come off, regardless of what they might have done, as the real innocents.