Nic and Jules (three-time Academy Award nominee Annette Bening and four-time Academy Award nominee Julianne Moore) are married and share a cozy suburban Southern California home with their teenage children, Joni and Laser (Mia Wasikowska and Josh Hutcherson). Nic and Jules -- or, when referred to jointly by Joni, Moms -- gave birth to and raised their children, and built a family life for the four of them. As Joni prepares to leave for college, 15-year-old Laser presses her for a big favor. He wants Joni, now 18, to help him find their biological father; the two teenagers were conceived by donor insemination Against her better judgment, Joni honors her brother's request and manages to make contact with  bio-dad Paul (Mark Ruffalo), an easygoing restaurateur. The kids find themselves drawn to the confirmed bachelor's footloose style -- especially in contrast to Nic, a principled doctor who has long established their house rules. Jules, who has been looking to start a new career in landscaping, also strikes up a rapport with Paul. As Paul comes into the lives of the forthright four, an unexpected new chapter begins for them as family ties are defined, re-defined, and then re-re-defined.