"Parenthood" is a wonderful experience, because it does what comedy (at it's peak) does best: tell us the truth, with all it's humour and aching.
Essentially the plot is basic: Steve Martin's extended families encounter their various trials and joys in trying to raise their kids. But the plot isn't the real driving force here - it's the beautifully observed characters, written with reality and acted with integrity, that elevate the piece. Jason Robards is great as the emotionally conservative father with a soft spot for his tearaway youngest; Dianne Wiest as a single mother whose brave face keeps slipping; Rick Moranis as the ultimate competitive father; and of course Steve Martin as the Everyman who Doesn't-Want-to-Turn-Out-Like-My-Father. The way the script keeps shifting gears between the light hearted good times families enjoy through to the deep undercurrent of perpetual pathos explodes family life better than almost any film you care to mention.
Some may find parts of the film a little too sugary, and although I can understand this view (we all hate sentimentality dribbling on genuine depictions of love) I'd have to disagree: the film doesn't end with a neat "everything is always sunny" denoument. The moral, ultimately, is that the when you get up close, everyone in a family is "dysfunctional" on some level, but that doesn't stop them being your family, and it doesn't stop you loving them.