As moviegoers became exhausted by Hollywood blockbusters, independent movies grew in popularity. Unfortunately, indie films began to wear down audiences with their own brand of overdone quirks and cliches. Thus was born mumblecore, an intensely low-budget independent subgenre defined by naturalistic dialogue and performances that attempt to bring reality back to indie cinema.

Lynn Shelton and Mark Duplass are two of the more popular members of the mumblecore movement. Their latest effort, the family drama "Your Sister's Sister," fits nicely into the genre with its extended, often improvised conversations and low-budget origins. It's a small film that I doubt will turn many mumblecore critics into converts, but it's a warm, well-acted movie that can kill 90 minutes painlessly.

Duplass stars as Jack, a schlubby, unemployed 30-something who is struggling to get over the death of his brother a year ago. His best friend, the delightful and patient Iris (Emily Blunt), tries to get Jack to break out of his downward spiral by sending him to her family's excluded island cabin to refocus his life. It seems like a smart plan (or the start to a generic horror movie) until Jack arrives at the cabin and finds Iris' sister Hannah (Rosemary DeWitt) is already occupying it, nursing her own emotional wounds with some alone time and a bottle of booze.

The two drunkenly bond, resulting in a sloppy one-night stand. Things get complicated the next morning when Iris, who is starting to view Jack as more than just a friend, unexpectedly shows up.

Writer/director Lynn Shelton creates a comfortable tone for her family drama, filling "Your Sister's Sister" with inviting shots of the northwest coast and its beautiful forests. Even the characters, especially Blunt, are perpetually costumed in cuddly sweaters and hats. It creates the sensation of a big warm cinematic hug.

Shelton also avoids one of mumblecore's most notoriously irritating attributes: the handheld camera. Many films in the subgenre's library (including Duplass' own "Jeff Who Lives at Home" from earlier this summer) feature obnoxious shaky camera shots with distracting shifts in focus. "Your Sister's Sister" includes almost none of these stylistic traits and, as a result, feels like a more confident and immersive movie.

Adding to the comfort factor are the performances. Duplass, who, with roles in "Safety Not Guaranteed," "People Like Us" and December's "Zero Dark Thirty," is having a career year, charms the audience with his easy-going, articulate oaf persona. He holds his own during the film's dramatic moments as well.

Rosemary DeWitt (having a busy year of her own with "The Watch" and "The Odd Life of Timothy Green") is excellent as well as Hannah, Iris' testy lesbian sister. She always feels real and sympathetic, even when a late twist casts a devious light on her seemingly innocent hook-up with Jack. Blunt sparks nice sibling chemistry with DeWitt (despite her British accent, which is explained away in a sentence or two) and romantic chemistry with Duplass.

As "Your Sister's Sister" goes along, however, I found much of my overall enjoyment waning. The pacing, which felt so natural in the first half of the film, began to feel glacial as conversations and plot developments dragged themselves out. Even the score, filled with mysterious chimes and bells, turned from a minor quibble into a significant annoyance. It's the kind of forced quirk that a movie like this certainly does not need.

The biggest place where Shelton's film stumbles is the story's shift in attention. The movie's best and most honest moments are related to the sibling drama, not only between Iris and Hannah, but also between Jack and his deceased brother. An early memorial scene involving an uncomfortably unflattering toast by Jack is captivating in its honesty.

Unfortunately, as the script goes on, the contrived romantic triangle angle gets most of the attention while the family drama, and a serious late development involving Hannah's true intentions, get pushed aside. The sisters' problems get resolved with a montage, while the petty love story and Jack's underdeveloped journey to maturity get the big dramatic speech. Hannah's personal dilemma gets even less resolution.

Even when it gets trivial and languid, however, the movie's sweetness helps it go down smoothly. "Your Sister's Sister" is indeed flawed, but whose family isn't?