Earlier this year, a movie came out that purported to examine contemporary feelings about adoption. The dour Mother and Child was oddly conservative in its insistence that every child needs its biological parents. Now, along comes a film that acts as a timely corrective to Mother and Child's moralizing: Writer/director Lisa Cholodenko's (Laurel Canyon, High Art) excellent The Kids Are All Right does full justice to the complexity and flexibility of the modern family.

Teenagers Joni (Mia Wasikowska) and Laser (Josh Hutcherson) have two moms: serious, uptight Nic (Annette Bening) and flighty dilettante Jules (Julianne Moore). The kids were conceived via artificial insemination, both from the same sperm donor; their family life is functional in the dysfunctional manner of any household inhabited by multiple teenagers.

When Joni turns 18, her younger brother urges her to seek out the identity of their donor. A few phone calls later, the kids are having dinner with their biological father, Paul (Mark Ruffalo). Dinner is excruciatingly awkward, but Paul's good intentions are clear—when Laser asks him why he decided to donate sperm, Paul struggles to provide the kid with an origin story more meaningful than "I needed the cash."

Nic and Jules are initially suspicious of Paul's interest in their kids, and disappointed to find that the man who was studying international relations when they selected his sperm went on to drop out of college and open a restaurant. (While Kids is essentially an extended ad for gay marriage, Cholodenko doesn't spare these middle-class lesbians scrutiny; their snobbery and pretense provide much of the film's humor.) Jules soon warms to him, however, and shortly thereafter, the two begin an affair (brace yourself for a scene in which Jules, who's been in a relationship with a woman for 20 years, goes crazy for cock). After years of bachelor living, Paul convinces himself that he's ready to become a family man—and the family he wants is Jules and the children.

There's a horror movie premise buried underneath Kids' bobo veneer—witness Nic's growing discomfort with the role of Paul in her family's life, even as the audience is privy to how much worse things are than Nic suspects. But this is no Fatal Attraction, and Ruffalo's rumpled character is basically decent—his flaw is that he thinks he can take a shortcut to adulthood, stealing the things he wants instead of earning them. This is a film that allows its characters to be complicated, and it's quietly revolutionary in its upending of the conventions of the cinematic family.