THE opening declaration “based on a true story” has become so commonplace in cinema one half expects to see it on the next Star Wars. In the case of Sean Anders’ comedy about adoption it really is true, and that matters.

It matters because Instant Family goes to places other family comedies rarely dare to venture. Sometimes this works, sometimes it does not, but the film’s heart is in the right place, and one can see why the picture is being championed for its honesty by organisations working in this area.

Pete and Ellie (Mark Wahlberg and Rose Byrne) have a great life together doing up old houses and selling them on for a profit. The only other heartbeat in their house belongs to the dog. One day, Pete jokes that he wouldn’t want to be an old dad so maybe they should adopt a ready made brood. Ellie, though, takes him seriously and before you know it they are in a room with other adoption hopefuls undergoing assessment and training.

Despite having no experience with children, they take on three, the eldest a teenager. Lizzy, Juan and Lita (Isabela Moner, Gustavo Quiroz, Julianna Gamiz) are sweetness and light on the first visit. How hard could this be, think the couple. “We got lucky,” Ellie tells the support group meeting later, wondering why all the other parents are laughing.

True enough, reality kicks in. At one point, things get so bad the couple discuss giving the children back to social services. This is bleak, bold stuff, and does not make for comfortable viewing. Perhaps only someone who had walked the adoption walk, as Anders has, could get away with it, and it helps, too, that it is Wahlberg (Ted) and Byrne (Bridesmaids), two performers known for their way with edgy comedy, delivering the lines.

Another of the film’s saving graces is the partnership of social workers Karen and Sharon (Octavia Spencer and Tig Notaro), who run the programme. They are a wonderful blend of gallusness and plain speaking, with Spencer having the lioness’s share of the film’s best lines.

So far, so good. Anders, besides being a father to three adopted children, is also the helmer of the Daddy’s Home comedies and other films hardly famed for their subtlety. Given the chance to take a joke too far, he grabs it. He also has a yen for slapstick, which plays out badly for the Juan character, a kid who is always in the wrong place at the wrong time when it comes to accidents.

Not every joke works, some scenarios should have been ditched early on, and despite the aim to keep things real, the film is not without sentimentality.

But that’s Instant Family, a film that comes with all its flaws easy to see and just as easy to forgive.