Gather the family grownups for an affectionately funny Christmas with The Family Stone, a dramatic comedy that winds its way around numerous obstacles thanks to writer-director Thomas Bezucha. He takes an ordinary premise—holidays with the family—and injects an amusing and powerful elixir.

With a dynamite cast, Bezucha gets a lot of help, deploying the tried and true personas of an all-star roster to good effect. Leading with Diane Keaton as the brood's acerbic, East Coast liberal mother, Stone starts with her gazing into space with something heavy on her mind before the Stones assemble for another Christmas. It is an upper middle class affair, politically correct in a superficial and charming way—which is possible, as Bezucha carefully demonstrates—and, with Craig T. Nelson (aged to perfection) as the spouse at her side, Keaton as matriarch is in top form.

So is everyone else, which includes Ty Giordano as deaf son Thad, half of the obligatory gay couple—Brian White is the other half as his angelic partner, Patrick—Elizabeth Reaser as daughter Susannah, keeping a secret, like her mother, and better known players as their siblings: Rachel McAdams as troublemaker Amy, Luke Wilson as stoner Ben and Dermot Mulroney, as Everett, the good son.

Everett brings uptight Meredith (Sarah Jessica Parker) home for the holidays, and, after stating that he intends to pop the question—seeking the family's approval, symbolized by a ring—he reminds his mother that she pledged to bestow the heirloom after he'd chosen a bride. Delivering the funniest line, she bluntly changes her mind.

Most of the humor involves Meredith, a high achiever who wears her hair in a bun, insists on sleeping in separate bedrooms and is less than believable as someone deserving of Everett's affections. However, the Stones and their dysfunctional dynamics are played with the right blend of recognizable behaviors to make Meredith acceptable as their comic foil. Impetuous Amy (McAdams as a viper) skewers Meredith, egged on by Keaton, who adds her own digs, while hubby Nelson frets over whether Everett is his own man—nice to see a dad with a brain, for a change—while gay couple Thad and Patrick make like a Martha Stewart special, brewing coffee, baking, cooking and being too good to be true.

Meanwhile, Meredith—who exhibits a sincerity the Stones lack—has had it, and she decides to head for the nearest motel, having stepped on everyone's toes and exhausted every tactless cliché involving blacks, gays and the handicapped. Stone bounces happily along with the frivolous flair of an NBC sitcom, which means none of it is completely plausible, especially when Meredith smashes the car and falls apart—with pothead Wilson coming to the rescue.

Calling upon her levelheaded sister (Claire Danes), Meredith and Everett stall and, with opposites attracting, secrets showing, and snotty sister McAdams getting just deserts, it is shaping up as one, big, horrible Christmas. But Bezucha saves the best for last, playing the beautiful song, "Have Yourself a Merry Little Christmas" from Meet Me in St. Louis, and suggesting that what constitutes family are shared, united values that can't be forced or faked.

With lots of dry laughter, The Family Stone makes it easy to miss its little lessons in love, acceptance, the loneliness peculiar to Christmas—that first Christmas after the death of a loved one or during a divorce—and what's among the prized virtues in any good family: independence. With that, this warm Christmas movie captures the true meaning of making room for one more. Scott Holleran