It continues to amaze me that grown-ups are able to tend to their romances while going about the everyday business of raising a family. Despite the obvious joys, long-term commitment can be a minefield of miscommunication and resentment, with that mutual love the only armor against the ego-piercing shrapnel. Throw children into the mix, and the possible damage is hardly collateral. So of course more films are drawn to the breathless thrill of getting together than the art and diplomacy of staying together; eye-candy escapism sounds way more appealing than two hours of someone just like you fretting over the checkbook or pouting about sex. But there is clearly much drama and humor to be found in something so seemingly mundane; the trick is making the fiction compelling while staying truthful to our common realities.

So in an age when too many relationship comedies err on the side of zany contrivance, Lisa Cholodenko's wise, witty "The Kids Are All Right" feels like a blast of uncut oxygen. Annette Bening and Julianne Moore star as Nic and Jules, an established Angeleno couple and mothers to two teenagers whose familiar routine is shaken up when their children get curious about their origins. After a call to the sperm bank by college-bound Joni (Mia Wasikowska, "Alice in Wonderland") on behalf of her 15-year-old brother Laser (Josh Hutcherson), into the family orbit swaggers the ultra-groovy Paul (Mark Ruffalo), organic farmer, restaurateur, and donor of seed. No one is quite sure what to do with this new male energy, which pinballs among paternal, scampish, and sexy, and though the kids obviously blossom with Paul's attention, simmering problems between Nic and Jules reach their boiling point.

Not that things between the two were entirely harmonious to begin with; Nic is a doctor whose love for red wine is inching from affinity to dependency, while Jules has been a bit unfocused careerwise now that the kids are relatively grown. And when Paul becomes the first customer in Jules' fledgling landscape-design business, he seems to see in her a kindred lost soul as well as the earthy domesticity that this 40ish ladies' man believes he now wants. "The Kids Are All Right" unfolds as each member of the family tests their boundaries, learning painful lessons in the process and reaching individual epiphanies. That it explores issues like infidelity, aging, and parenting in such a universally observant way serves subtle notice to the conservative killjoys who are convinced that same-sex marriage means the end of the traditional American family.

Which isn't to imply that "The Kids Are All Right" is even remotely political. Cholodenko, working from a funny, huge-hearted script that she co-wrote with Stuart Blumberg, manages to make the sexual orientation of Nic and Jules their least compelling detail. They have the same problems that any married, middle-class parents might have, and they're as ill-equipped to cope with them as their hetero counterparts. And though it's clear Ruffalo was hired because Paul is so Ruffalo-y, Cholodenko couldn't have chosen a better central pair. Bening's second act has yielded a previously untapped vein of steely vulnerability, and Moore makes Jules' confusion utterly sympathetic while showcasing her little-used flair for comedy. The two women meld beautifully, capturing the love, faith, and hard work required to devote yourself to another human, legally or otherwise.