Featuring Matt Berninger and the National. Rating unavailable.

“When we agreed to be in your documentary, we thought you were going to ask some questions about us.” So states a member of the National, a mid-level indie-rock outfit with two sets of brothers and lead singer Matt Berninger, a charismatic frontman given to bouts of introspective stage frenzy.

Matt has a brother, too: the recipient of the opening quote and a walking case of arrested development. Nine years younger than Matt, and a somewhat porky metalhead who hates alternative music, Tom Berninger at 30 is still living in their parents’ Cincinnati basement. His social skills stink, but he has some filmmaking ambitions. (His homemade horror chops are a notch above those of the dude seen working on “Coven” in American Movie, to which this breezy, 75-minute doc can be compared.)

With the help of Matt’s wife, Carin Besser, a former editor at the New Yorker, Tom gets hired as a roadie for the band’s 2010 High Violet tour. Aside from sticking his consumer-grade Canon in everyone’s faces and asking inane questions (“Do you ever get sleepy on-stage?”), Tom drinks up the band’s booze budget, tries to horn in on their photo op with Barack Obama, and misses the tour bus at one point. Things blow up in Los Angeles, when Tom loses the guest list just before a big show. “Who was on the list?” Matt angrily demands. “I dunno,” the flustered bro answers, “I think it was Carin’s parents, Werner Herzog, and the cast of Lost.”

It’s hard to say how much the budding filmmaker was playing up the Little Tommy Fuckup persona for his own camera. But as a cataloguer of obsessive sibling rivalry, he definitely has talent. And despite the guy’s best efforts to make Matt and the people around him look bad, what we get in Mistaken for Strangers is a surprising amount of patience and forgiveness. Plus a pretty good beat.