Amherst is a small college; the student population here hovers around 1,700. That means there are slightly less than 500 people per class. Imagine if all 500 of them were biologically related to you. Five hundred siblings — and you thought your one younger brother was bad enough — creepy, right? This is the premise of writer-director Ken Scott’s “Delivery Man,” the American remake of the 2011 French-Canadian comedy “Starbuck,” also directed by Scott.

Vince Vaughn is David Wozniak, a forty-something deliveryman for his family’s butcher shop. He’s the stereotypical “lovable, middle-aged slacker” character: he has a good heart but his priorities aren’t quite in order. David lives in a dingy apartment in New York City, a few blocks away from the Wozniak family business. It’s clear from the overdue notices plastered around his living room and kitchen that he’s not so conscientious about paying bills. He owes $100,000 to some sketchy-looking mobsters (in a side plot largely unexplained throughout the course of the film), and he starts growing pot in his apartment in attempt to settle his debts. Emma, his police officer girlfriend (the serviceable, but largely forgettable Cobie Smulders) reveals that she is pregnant, but prefers to raise the child on her own because David is just too unreliable.

David’s life continues with its downward trend as the film progresses. In a montage of scenes, the audience watches David get scolded by his father and brothers, receive two parking tickets and dejectedly observe his delivery truck as it is towed away. He returns from a hellish day at work to find a strange man in his apartment, who informs him that he is — surprise! — the biological father of 533 children, 142 of which have taken legal action to find their second parent’s identity. David, we learn, made 696 sperm donations under the pseudonym “Starbuck” in an effort to make some quick cash in his 20s. Despite the confidentiality clauses he signed before each donation, he’s now involved in a lawsuit with more than 100 young plaintiffs and must employ the help of his equally loserish, incompetent lawyer friend, Brett (Chris Pratt, who is a bright spot in a comedy that is never all that funny) to keep his identity under wraps.

Brett, a single parent of four, warns his friend not to open the 142 envelopes containing the profiles of his biological children — the less David knows about them, he says, the better. David, of course, can’t resist. The first envelope he opens contains a picture and biography of a star basketball player on the Knicks! He goes to his son’s game that night, of course. In the style of a sappy Lifetime movie or a Hallmark card commercial, David tracks down the young adults in the envelopes (most of whom miraculously seem to live in the New York metropolitan area) and makes sure to have an interaction with them. He tells Brett that he can’t be the father to all of them, but he can act as their “guardian angel.” In yet another montage of scenes, David helps an aspiring actor audition for the role of a lifetime, ushers a heroin-addicted teen to a treatment center, attends a museum where one of his “kids” is a tour guide and makes a scene in at the YMCA so his lifeguard “son” can save him. In one of the few genuinely touching segments of the film, he visits his mentally challenged son in a group home and promises to visit regularly. These interactions are David’s attempts to redeem himself, to give direction and purpose to his aimless (and pretty bizarre) existence. He even renews ties with his pregnant girlfriend, who agrees to let him help her raise their baby, as long as he continues to piece his life together. Things seem to be looking up for David, and his only remaining obstacle is to win his lawsuit so his life can return to normal. The rest of the film proceeds with some mildly funny dialogue and cliché courtroom drama.

David, in these scenes, is never completely likeable: I consistently got the sense that he performed each act of kindness towards his “children” for self-gratification, to ease the mild sense of guilt he had for not being involved in all 533 of their lives. This brings up another question, however — why should David feel obligated to involve himself in their lives, anyway? The reason why the confidentiality clauses he signed were moot is never adequately explained. I spent the majority of the film in frustration, wondering how the lawsuit could have even been filed in the first place. While “Delivery Man” has some nice scenes about the varying meanings of “family” and how we can seek support and companionship in unconventional ways, it would’ve been even better if the difference between “father” and “sperm donor” was actually explored.

Despite a unique premise, “Delivery Man” relies on the clichés of countless genres to keep itself moving. While watching, I detected hints of the slacker movie, the romantic comedy, the courtroom drama and the preachy family movie. Therein lies one of “Delivery Man’s” flaws: it can’t really decide what kind of film it is. The script, especially the first half hour or so, is slow moving. And for a film classified as a comedy, I can count on one hand the amount of times I laughed aloud.