Every family has an Uncle Berns, or should.

The official patriarch of the Billy Crystal clan is Bernhardt “Uncle Berns” Crystal, a garrulous 88-year-old man-child too enthralled with life to fade into the sunset.

His official biographer turned out to be his great-niece Lindsay Crystal (Billy’s 25-year-old daughter), whose documentary “My Uncle Berns” is a loving, if slightly overweight, tribute to a remarkable man.

The film makes its premiere on HBO on Thursday, Aug. 5.

For a first-time filmmaker, Lindsay Crystal is remarkably self-assured. Then again, with her father serving as executive producer (and, no doubt, financier), she was able to snag a top-flight crew to help her out.

With its mix of vintage photos, home movies, talking head interviews and dazzling animation, “My Uncle Berns” looks and sounds as good as a film from that other Burns, (documentarian Ken Burns).

But it is the outsized personality of Uncle Berns that gives the film its heft. The old man is so funny, warm, loving and deep, he could have carried the movie by himself, however small the budget.

“My Uncle Berns” video review begins with the events of Sept. 11, 2001. Berns is living in a senior housing complex a block away from the World Trade Center. Crystal’s camera captures the collapse of the towers, and she wonders if Berns is all right.

Fortunately, all the residents had been evacuated safely, but the filmmaker’s panic opens the window to her great-uncle’s past. Reared in a Yiddish-speaking Brooklyn family, Berns was a child of the Depression. He recounts the death of a beloved sister, his mother’s subsequent temporary psychosis (during which she blamed her son for the girl’s death) and his years as a teen runaway.

A strapping, handsome devil, Berns later enlists in the army to fight the Germans. A chance encounter with Gen. Dwight Eisenhower leads to his drawing a series of war bonds posters, launching his career as an artist and gallery owner.

The war sequence is among the film’s best. Blending stock footage (Berns stormed Omaha Beach) and Berns’ own artfully animated sketches, Lindsay Crystal captures D-Day as never seen or felt before.

Berns’ wartime experiences seem to have squashed his religious inclinations. But there’s something so beautifully, overwhelmingly Jewish about him and his family, it’s no surprise that Billy Crystal, hip as he is, always seemed to embody the comic traditions of the Lower East Side

Berns’ artistic talent forms the heart and soul of the film. His pen-and-ink style falls somewhere between Maurice Sendak and Hieronymus Bosch, but remains wholly original. His greatest career success came as a Manhattan gallery owner and consigliere to artists, many of whom pay on-screen homage to the man.

Equally important is Berns’ sense of humor. He’s a prodigious cornball who spread laughter wherever he went. No prop was too silly for him: African masks, fright wigs, tubas, anything for a laugh.

This makes for some delightful viewing, but director Lindsay Crystal doesn’t quite know when to stop. There are so many scenes of Berns’ clowning, it becomes tedious after awhile. In comedy, as in documentary filmmaking, less is more, and “My Uncle Berns” is in need of a ruthless editor.

Over the course of the film, she shows Berns’ physical deterioration. Aging is hard on him. But despite the setbacks, Berns is never down for the count. He’s ever ready with a joke to lighten the mood.

Props go to composer Christopher Libertino, whose jazz-inflected score provides the right light touches. And director Crystal’s judicious use of animation shows she has the makings of a beautiful mind.

But most credit goes to Berns himself, a model of how to grow old with grace and, in his case, with hilarity. Like the Mozart character from “Amadeus,” what will likely endure of Uncle Berns is the laughter. He’d probably want it that way.

“My Uncle Berns” premieres on HBO at 7:30 pm, Thursday, Aug. 5.