By Brian Lowry

CNN

(CNN) -- Gru's family keeps growing while the franchise's charms keep shrinking in "Despicable Me 3," a fairly laborious and chaotic addition to the hugely popular animated series. While the central character discovers that he has, perhaps inevitably, an evil twin, the fraternal bonding that ensues isn't despicable as much as simply tiresome.

The cleverness that characterized the original film -- with Steve Carell as the villain whose hardened heart gets melted by a trio of orphans, and the colorful Minions stealing the show -- feels seriously diluted this time around. Indeed, the writers actually have to concoct a separate plot involving the Minions, whose future as a solo act might be considerably sunnier than the flagship title at this stage.

Foremost, this third installment feels as if it's trying to jam too much into its relatively modest length. Not only is there a new over-the-top villain -- a former child TV star, Balthazar Bratt, voiced by "South Park's" Trey Parker -- but Gru tries to connect with his long-lost brother Dru (also Carell), while Gru's wife Lucy (Kristen Wiig) seeks to prove her mothering credentials to her stepdaughters.

Dru, moreover, has been raised in the faraway land of Freedonia (one suspects referencing the Marx Brothers will largely be lost on the target demographic), which temporarily shifts the action there. Eventually, the climax takes place in Hollywood, amid a fair amount of carnage as Bratt plots revenge against the town that discarded him.

Those rather inside jokes notwithstanding, unlike the Pixar movies the appeal to adults feels limited. Even the kids in attendance during an advance screening seemed notably antsy, perhaps because of the semi-arid stretches between the big slapstick and vaguely naughty sight gags that the gibberish-spouting Minions in particular provide, including a peculiar foray that lands them in prison.

Frankly, there's room for sympathy toward the stewards of such an enterprise, faced as they are with the challenge of piling fresh elements upon what already exists. The result, however, is an inordinately busy movie that yields a few amusing and even sweet moments -- a la Gru's young daughter and her quest to find a unicorn -- that are largely snowed under by the loud and obnoxious ones.

So while the first movie was, as noted, at its core rather charming, for "Despicable Me," the third time definitely isn't the charm.

"Despicable Me 3" opens in the U.S. on June 30. It's rated PG.