The Scenes with Dianne West/Martha Plimpton/Keanu Reeves and Joaquin Phoenix are best stuff
I like Parenthood, Steve Martin is great but the films strongest element is the stuff with West divorcee sister and her teenager daughter Plimpton and angsty teenage son Phoenix. Throw into the mix Reeves, the stoner boyfriend of Plimpton with a heart of gold. Phoenix shows early signs there wasn't just one talented brother in the family, his scenes are heartbreaking. Reeves is great too.
But Dianne West got a well deserved Best Supporting Actress nomination for this too. She steals the film, the scenes when she finds out about the picture and Plimpton getting married are fantastic. A mother who loves her children but also wants to find love herself.
As a kid the Steve Martin stuff was the stuff I loved but as I got older and after a recent rewatch it's the Dianne West scenes where the film really shines.