When they meet 15-year-old Lizzy (ISABELA MONER), they're taken aback by her spunky attitude, but also drawn to that, and while they envisioned getting an infant, they think the teen might be the right fit. What they weren't expecting is a package deal in the form of her younger siblings -- tentative and nervous Juan (GUSTAVO QUIROZ) and bratty Lita (JULIANNA GAMIZ) -- but decide to go for it anyway.

At first, it works out beautifully, and Mark's mom, Grandma Sandy (MARGO MARTINDALE), and Ellie's parents, Jan (JULIE HAGERTY) and Jerry (MICHAEL O'KEEFE), enjoy their new foster grandkids. But once the honeymoon phase is over, Pete and Ellie quickly realize that parenting is a lot harder but also more rewarding than it appears, especially when they've become an instant, five-person family.

All of those and more simply point out the universal truth that no matter how prepared one might think they are to undertake pretty much any endeavor, things will always come up to undermine them. Take, for instance, people who are about to become parents, be that via the old-fashioned way or through adoption.

Whether it's through reading books, talking to others or simply thinking they've got the trick figured out, some believe they know exactly what to do to make it a stress-free experience. Seasoned parents, of course, simply respond to such assertions with a knowing smile (or grimace) and a simple "Uh-huh..."

Imagine, though, if instead of suddenly finding yourself as the parent to one you end up with three kids all at once. Yes, some people end up with triplets, who can obviously be more than a handful to care for and, later, corral. But what if said kids consisted of a rebellious teenager, her overly sensitive younger brother who's easy to apologize if not outright cry, and his even younger, bratty sister? That's the gist of "Instant Family," a comedy that, as the title suggests, revolves around adults suddenly in the custody of kids.

And for writer/director Sean Anders -- who co-wrote the script with John Morris -- the offering stems from his own experience of adopting three kids with his wife a few years ago. The result, while broadly played -- which shouldn't come as a surprise considering he's also directed the likes of the two "Daddy's Home" movies along with the likes of "Horrible Bosses 2," "That's My Boy" and "Sex Drive" -- and near constantly teetering on the brink of being both manipulative and maudlin, manages, for the most part, to work.

The comedy is decent, the parenting issues come off as believable, and the old heartstrings are tugged on enough that you'd have to be a true movie Grinch not to fall prey to what's offered. And by repeatedly touching on some rather dark issues for a comedy -- including abused kids who end up in the foster care system, drug addiction, sexual abuse and so on -- it more than earns its humorous and heartwarming moments.

The story revolves around Pete and Ellie Wagner (Mark Wahlberg and Rose Byrne, making for a believable couple) who for one reason or another have put off having kids but now sense that perhaps that was a mistake. After they consider adoption and then look at photos of kids in foster care and hear their stories (and simple desires), they're heartbroken but determined to help one of them. After all, since they're good at rehabbing old homes and flipping them into a new and improved version of what was once there before, surely they can do the same to some broken kid.

Those running the local foster care placement service (Octavia Spencer and Tig Notaro) warn them and other would-be parents -- who repeatedly pop up in a running gag of such a support group -- that it's not as easy as one might perceive, but don't go as far as to drop the Tyson line about getting punched in one's parenting face.

Although she doesn't fall into their preconceived notion of the sort of child they would normally pick, they take a liking to 15-year-old Lizzy (a good Isabela Moner) despite (or perhaps because of) her straight-shooting attitude toward them. But she's part of a package deal, and once the childless couple sets sights on pics of their adorable mugs they're sold.

And then the fun begins, what with Lizzy being a typical moody teen, her younger brother, Juan (Gustavo Quiroz), being overly sensitive and prone to crying, and young Lita (Julianna Gamiz) being more than a bratty handful. The new parents try to cope, wonder if they've made the biggest mistakes of their lives, and everything tumultuously heads toward a predictable conclusion.

There are funny bits and touching bits along the way, as well as varied interactions with various family members, including Margo Martindale and Julie Hagerty playing decidedly different sorts of grandmas. As touched on before, much of what's present is broadly played, and if that sort of sitcomy material and aura grates on you, this might be a long two hours through which you'll sit.

For me, it all depends on what degree that quality is slathered onto such material. While I could easily see and sense it throughout, it and other issues here and there didn't bother me enough to offset the film's winning or at least entertaining and enjoyable moments. To go along with the opening quotes, I sort of went in expecting this not to be my cup of tea but then the story happened and I came out liking it. Nothing great but enjoyable and a bit thematically deeper than I imagined it would be, "Instant Family" rates as a 6 out of 10.