Lisa Cholodenko's drama-laced comedy The Kids Are All Right is generous and warm-hearted to a fault, though as faults go, that's one of the best to have. Examining the dynamics of a non-traditional family without message movie condescension, nor does it play up the quirky elements of the scenario; it's just so damn humanist I kind of can't get my head around it.

The story revolves around Nic (Annette Bening) and Jules (Julianne Moore), a couple with two children conceived three years apart, using sperm from the same anonymous donor. Joni (Mia Wasikowska) is 18 and just out of high school; her 15-year-old brother Laser (Josh Hutcherson) convinces her to use her newfound majority to contact the sperm bank from which their genetic material came, because he's been itching to meet his biological father for quite a while now. Joni is reluctant at first, but caves; and so the kids meet Paul (Mark Ruffalo), an organic farmer and locavore restaurateur who lives in the same part of town, in the script's single obvious and hollow contrivance.

Paul's presence is both refreshing and dangerous: Nic and Jules's marriage has been strained lately, and having to deal with the fact that their children suddenly have a new father figure isn't helping matters out one bit. Especially once he hires Jules (who has been trying to start a landscape design company) to make-over his new backyard, and she starts to take his side against Nic, a little bit. Things are awkward and funny, then unpleasant and less funny, and always have the bit of truth.

Representational issues aren't my forte (and The Kids Are All Right introduces some very specific issues that no male should feel entirely comfortable discussing in absolute terms), but to ignore them in this case would be a case of willful blindness. It's bracing to see a movie in which a long-term homosexual relationship is presented so damn casually: absolutely nothing about the film proclaims itself as a "lesbian issues" picture. Rather, the particular, and terrifically compelling, dramatic situation that Cholodenko and co-writer Stuart Blumberg explore can only exist in the presence of that kind of long-term relationship, which is thus presented in an offhand, normalised way. The movie isn't about these women because they're lesbians; it's about these women because they go through a crisis as parents and partners. Their lesbianism isn't incidental, but it's absolutely not the point.

There's another point that I absolutely can't bring up without throwing up a paragraph-long SPOILER WARNING; eventually, Jules starts to have an affair with Paul, and this point has reasonably earned ire from some corners, although I think they're missing the point. Cholodenko has a child with her partner, Wendy Melvoin, which leads me to doubt that she is seriously trying to argue that all a lesbian needs is some hot Ruffalo cock; she's making the brave, mature, and wise argument (i.e. she's reaffirming what I've believed all along) that sexuality is a fluctuating continuum, not a series of concrete boxes, and who you do which act with isn't necessarily a referendum on who you are. In the film, Jules doesn't sleep with Paul because she's suddenly not a lesbian; she's lashing out at Nic, and Paul is merely the one who's there, and on her side, the relationship is strictly physical and devoid of emotional content.

But enough gender-politicking; it's out of my pay grade. I'm much, much happier talking about the kindness and sincerity with which the film portrays a group of people dealing with life's customary inability to go the way you want it to. At heart, this is a story about how tough it is to keep from being bored in love; a theme that movies, with their emphasis on passion, don't like to pay much attention to. But in the filmmakers' fine etching of Nic and Jules, we have here one of the most satisfying and realistic depictions of an old married couple to come along in ages. Bening and Moore both brought their A-games to set: Moore hasn't been this good since Far from Heaven, and I'm tempted to suggest that Bening has never been this good. The script, admittedly, tends towards the unsubtle in its depiction of these women (Nic is hard-edged and controlling! Jules is addled-minded and unsure of herself!), but the actresses - Bening especially - go right ahead and play the roles as if they were more subtle, and so the characters come across with fulsome vitality and realism.

They're not alone in giving great performances: in fact, as good as they both are, I'd still be inclined to tip the best-in-film notice to Ruffalo, whose characterisation of Paul borders on the miraculous. It's not his film, although Cholodenko, in her infinite generosity, makes sure that we spend plenty of time getting to know him; but as the actor digs into the role, it's hard not to wonder if he doesn't have the most fascinating arc. A satisfied playboy who is more or less happy with his life as it stands, Paul's response to finding out that he has kids, after a fashion, is a slurry of emotions from pride to the dawning awareness that he doesn't have anybody: Ruffalo embodies all sorts of conflicting impulses, and in his best moments - such as his first meeting with the kids, where the actor does more with the set of his brow than plenty of others could do with their whole bodies, and it's both touching and absolutely hilarious - he makes the character almost uncomfortably real.

(Also, while I'd never call her the equal of the three grown-up stars, Wasikowska is good here in a way that borders on the inexplicable following her dead-eyed approach to playing the unlikable heroine of the tedious Alice in Wonderland directed by Tim Burton).

Throughout all of this, Cholodenko refuses to pass judgment on any of these characters, though she absolutely does not obviate any of them from their guilt in the messiness that comes about. There are certain films where it's absolutely certain that the director loves her characters: this is very much such a film, which possesses a deep understanding of the way that humans work and more often don't work quite as well as we'd like. It's all in the title: The Kids Are All Right, while it obviously suggests the rejoinder "But the Adults Are Fucked-Up"; yet at the same time "all right" doesn't just mean "alright", it means "nobody is wrong". And while Nic, Jules, and Paul aren't kids, it seems hard not to find that they're covered by that warm blanket statement. They all make stupid damn mistakes; but we're never once invited to look down on them as a result.

That the film is lovable and exceptionally well-observed is undeniable; but it stops just short of being a masterpiece. For one thing, it's a little bit too eager to make sure we get exactly what's going on, and Cholodenko isn't afraid to have a character state themes outright just in case we missed them before (Moore's big Oscarbait moment is just such an Aesop moment, though she's on fire enough to carry us through). For another, the script does all of the work. Jeffrey M. Werner's editing is extremely tight, and Igor Jadue-Lillo's cinematography uses the southern Californian light well, and the score, with contributions by Carter Burwell and the band Shudder to Think, has a meloncholy jangle that compliments the action well; but Cholodenko seems vaguely unwilling to bring any real sense of cinema to bear on the story. It's as though every formal element of the movie was designed specifically to stay out of the way of the screenplay; it robs the film of some added resonance that would make it truly excellent, instead of just very, very good.

For very, very good it is: not too many films this year have left me feeling so pleasant inside, without anything cloying or artificial; it's as funny as any other movie to come out in months; it showcases some brilliant performances. My biggest complaint is that it should have been even better, which isn't criticism so much as grousing, but there you have it. At any rate, The Kids Are All Right is one of those "restores your faith in American indie cinema" moments, and God bless Lisa Cholodenko for that.