’Tis the season for festive comedy-dramas about awkward and/or farcical homecomings. There will be worse ways to dodge the high-street rush than this genial, Christmas-set Irish indie, in which hotshot Boston lawyer Daniel (Michiel Huisman) returns to his native Cork after his mother’s death to chaperone autistic teenage brother Louis (Samuel Bottomley).

Writer-director Aoife Crehan acknowledges a certain debt to Barry Levinson’s once prizewinning, now unfashionable Rain Man early on, and proves no less upfront about her dramatic contrivances. The first act is a blizzard of twaddle designed to get the brothers and mortuary assistant Mary (Niamh Algar) into a Volvo bearing a coffin containing the body of the stranger Daniel sat next to on his flight. Weather that, and you can settle in for a middle-of-the-road road movie across a drizzly, provincial Ireland: gently heartwarming, mildly amusing, only vaguely related to real life. Inevitably, family secrets are unearthed and worked through en route; inevitably, the two grownups have a moment, then a tiff, before pushing on towards reconciliation.

Crehan knits it together like a well-worn onesie: you know exactly what shape it’s going to be once you’re wrapped up in it, but that doesn’t mean it lacks for comfort and warmth. Odd surprises keep it from terminal predictability: there are a couple of pretty good gags related to Louis’s soup habit, and a thoroughly unexpected revival of the comedian Denis Leary’s 1996 single Asshole, which appears to have stuck around in Crehan’s head longer than it did in the charts.

The performers, meanwhile, roll up the sleeves of their winter wear and strive to lend inherently thin material what heft they can. Huisman putters along in a blandly personable second gear, but Bottomley is sparkier, and there’s another useful profile boost for Algar, so compelling in Shane Meadows’ The Virtues on TV.

• The Last Right is released in the UK on 6 December.