Since the birth of Louise Brown – the world’s first “test-tube baby” – the creation of families has become ever more medically, ethically and emotionally complicated. Scant attention has been paid in movies to the complexities and the inherent drama and comedy of truly modern families. The Kids Are All Right does it; it’s a funny, honest, affecting portrayal of a family, of a couple and of kids spreading their wings.

It is, among other things, about a completely ordinary family in which the kids were conceived with a little help from an anonymous sperm donor. Joni (Mia Wasikowski) and Laser (Josh Hutcherson) are teenagers. She’s about to leave home for college, and he’s spending more time with his bullying, knuckleheaded friend Clay (Eddie Hassell) than his Moms would like. The kids’ Moms, Jules (Julianne Moore) and Nic (Annette Bening), are, like lots of couples married a long time, engaged in a constant renegotiation and reassessment of their lives together. They drive a Volvo. They worry about their kids like devoted helicopter parents do. They are starting to fret over the emptying of their nest. What their kids think about is a bit of a surprise to them: Joni and Laser want to know about their donor Dad, and secretly arrange to meet him.

Donor Dad is Paul (Mark Ruffalo), a scruffy, charming bachelor restaurateur and organic farmer. Joni’s wildly impressed by his locavore/organico cred; Laser’s not so sure, although Paul’s motorcycle might win him over. Paul’s existence as a freewheeling and sympathetic outsider – more like a cool older cousin than a father – and his sudden presence in the family’s settled, comfortable and routine life are an instant and potentially troublesome disruption. Complications ensue.

Directed by Lisa Cholodenko (who co-wrote it with Stuart Blumberg), The Kids Are All Right is more than all right. The script is insightful, heartfelt and funny, and casually and nimbly navigates emotionally complex and occasionally uncomfortable terrain. The Kids Are All Right effectively plops the audience into the midst of a family-in-progress, and manages to tap into the underlying comedy of everyday existence. Cholodenko and Blumberg perfectly capture the way that, in a long-term relationship, conversations flow from a source far removed – part of an ongoing river of dialogical interaction fed by many streams (and occasionally tumbling through rough waters).

The characters are people you wouldn’t mind spending more time with, which sets them apart from the usual loudly dysfunctional families portrayed in movies. Nic is an ob/gyn and the family breadwinner, and she can be a bit caustic; while Jules is a kind of New-Agey, flaky project-starter who is still trying to find herself. They don’t communicate perfectly with each other or with their kids. Moore and Bening are superbly attuned to their characters’ quirks and rough calluses, their sensitivities and vulnerabilities and their inherent goodness. Their portrayals are honest, sympathetic and unadorned. (And while we’re on the subject of honesty, it’s nice to see two middle-aged actresses not only acting their age but looking it, and looking absolutely lovely.)

The plot complications occasionally veer toward the predictable, yet the characters are so real and engaging and the portrayals so honestly casual that the movie’s novelty – a lesbian couple with two kids conceived with donated sperm – all but evaporates. It’s not just that families like this are no longer that unusual; there is really nothing unusual about the family in The Kids Are All Right. They struggle with the same kinds of problems – boredom, routine, miscommunication, kids who don’t listen, parents who don’t understand – with which every family contends.

This is surely by design. There is no point at which it is a social or political issue for anyone in the movie that Nic and Jules are a couple, or that they have kids. If gay marriage is a contentious political or moral issue anywhere, it is not the issue in The Kids Are All Right, which is instead concerned with the drama and comedy of family life, the chafing irritations of the ties that bind and the soothing, healing balm that those same ties provide.