Ben Stiller in David Gordon Green Family Comedy

In what seems almost like a cleansing ritual after wrestling with studio horror franchises, David Gordon Green’s Nutcrackers sees the director return closer to his indie roots, observing characters that sprout organically from their rural or small-town environments. This cute fish-out-of-water comedy about the unexpected rewards of a found family tries to approximate the naturalism, lyricism and raw emotion of Green’s early works George Washington and All the Real Girls, but it’s too predictably sentimental to have a comparable effect.

The idea came from Green meeting the four spirited young sons of an old friend, and Leland Douglas’ screenplay appears to allow latitude for semi-improvisation from those boys, playing versions of themselves. That gives the film a disarming sincerity that dovetails with Ben Stiller’s sensitive, understated performance as an uptight Chicagoan thrust into the inconvenient role of parent. But the abundance of montages and exuberant slo-mo romps only underline the shortage of narrative substance.

Green acknowledges a debt to youth films like The Bad News Bears and Breaking Away, expressing his desire to tell a story without cynicism, in which the young characters are unencumbered by the usual movie-ish gloss. In that aspect, he succeeds thanks to the spontaneity of the Janson brothers, who are clearly in their element playing unruly, home-schooled pranksters and looking after the pets and livestock that roam freely in and out of the messy house.

Renamed the Kicklighters for this fictional experiment, they range from Justice (Homer Janson) who’s 12; middle child Junior (Ulysses Janson), 10; and 8-year-old twins Samuel and Simon (Atlas and Arlo Janson).

Another of the films Green cites as an influence is Uncle Buck, and Stiller’s Michael in many ways serves a similar function to John Candy’s title character in that comedy. Except that Michael is no boozing slob. But nor is he a classic Stiller neurotic. A joyless real estate developer, he rolls into Ohio in his ostentatious yellow Porsche expecting to sign a few papers authorizing the foster-family placement of his nephews — orphaned when both parents were killed in a car accident. But things don’t go so smoothly.

The kids are introduced breaking into a fun fair at night, hot-wiring one of the rides before a security guard wakes up to what’s happening and they bolt across a field, leaping exultantly into the air as they go. Michael is greeted with a bill for the damages they caused, as well as back-rent on the ballet studio run by his sister, the boys’ late mother. He’s also informed by family services agent Gretchen (Linda Cardellini) that the promising foster candidates she had been eyeing to take the boys have fallen through.

Michael, or Mike, as the brothers insist on calling him once they finally decide to speak to him, is less than thrilled to be stuck looking after four near-feral children instead of being back in Chicago finalizing a major real estate deal he’s been working on for six years. He knows nothing about them and all they seem to know about him is that their mother once said he was incapable of love.

The Kicklighter boys are a fun collective presence, maintaining a close-knit bond even if Justice sidles off into occasional solitude, nursing a crush on Mia (Maren Heisler), a girl from dance class. All but the eldest have long golden hair, which gives them an ethereal aura in contrast to the voracious appetite for chaos that makes them such a handful.

The Jansons being nonprofessional actors, their dialogue is often mumbled and lost. But they make up for it with the authenticity of their connection to the film’s world and their bone-deep unity as actual siblings, often all talking at once.

Douglas’ script stalls efficiently enough by teasing out the possibility of two different prospective parents (played by Toby Huss and Edi Patterson) initially eager to take in the brothers. But the template for this kind of heartwarming comedy is set in stone, so it’s clear from the outset that it’s only a matter of time before Uncle Mike loosens up and melts into his destined role of de facto dad. To the filmmakers’ credit, the formulaic aspects are never belabored, and the gentle hints of a possible romance with Gretchen are nicely underplayed.

There’s charm in the way Michael’s final walls of resistance are broken down, via a performance the boys stage in town of The Nutcracker’s Mustache, their own radical rewrite of the Tchaikovsky ballet. That also serves as a tribute to their deceased parents, a melancholy note of loss that otherwise goes mostly unexplored.

Perhaps in order not to give the boys too much heavy lifting in the acting department, the script generally is less interested in the brothers’ grief than in Michael’s rediscovery of a heart, an organ obviously not required in the soulless world of real estate. He lightens up over fond childhood remembrances of playing with his younger sister, a part of his life and a central figure in it that he had archived away.

Nutcrackers is not exactly robust as uplifting family comedies go, but for audiences willing to get in sync with Green’s free-flowing groove, the emotional payoff will be affecting.