OK, so I haven’t read the book or seen the movie on which Cheaper by the Dozen is based. But I’d bet the family dog never rooted its snout furiously in a kid-hating boyfriend’s crotch.

As obviously devoid of solid comedic content as it is hopelessly reductive with its “themes,” Cheaper by the Dozen is a sappy, ludicrous crock that just gets worse as it lumbers on and on.

What’s its life-changing lesson? No matter how old you are, moving or traveling to the big city turns you into a self-centered jerk that blows off fellow family members. But it can be cured by the coming-together of a sibling running away.

Given the movie’s telegraphing, that’s no spoiler. It’s either that or a car accident involving eldest brother Charlie (Tom Welling), given how often we see him driving his rickety Oldsmobile around.

It’s a truly classless movie in which to wallow for Steve Martin and Bonnie Hunt, playing the parents of 12 children. Once Hunt’s Kate leaves to pursue a book career, the household, like the movie, goes to hell. It then becomes an awful, sugary version of Martin’s own Parenthood, a movie that shames this one with its potent combination of comedy, poignancy and kids running around.

Martin plays Tom Baker, the college football-coach patriarch of the family that has 12 children ranging from tots to twenty-somethings. The opportunity presents itself for Tom to coach at his alma mater, Illinois Polytechnic College — sounding like a powerhouse football school if ever there was one. He packs up from a small town, moves to the Chicago suburbs and then subplots go bad.

There’s the son saddened at the way he doesn’t fit in the family (no surprise considering Tom can’t remember his name, for crying out loud). There’s Charlie’s anger at the city kids’ taunting. Oldest daughter Nora (Piper Perabo) wants her own life with selfish boyfriend Hank (Ashton Kutcher, he of the violated groin in an unbilled role).

And middle daughter Lorraine (Hilary Duff, still only good as Lizzie McGuire) is tired of receiving Nora’s second-hand clothes, even if these “hand-me-downs” resemble this year’s line at Express.

Excepting identical twins (Brent and Shane Kinsman) — notable only for their mean-spirited misbehavior that’s not at all endearing to the story — the rest of the clan is wallpaper. 

Apparently the Gilbreths, true-to-life parents of 12, were efficiency experts interested in human motion and human effort. Director Shawn Levy’s favorite human motion is vomiting and the only human effort comes from Martin and Hunt, who sadly get only one funny moment apiece. For Martin, it’s not when he yells “Pasta de la crotch!” as Charlie’s athletic cup sails into the red sauce.

Levy is horrible at making films but excels at persuading celebrities to send their images up in cameos. Who knows if Kutcher is perceptive enough to know he has the film’s biggest laugh? His Hank is an actor who acknowledges he has no talent and his face is the “moneymaker.” Hmm.

To borrow his MTV vernacular, if you fall for this “family film,” you’ve been punk’d.