Terry and Eric Fan are accustomed to collaborating. They’re brothers—Terry’s a year and a half older—and they’ve been making things together for decades. They were drawing before they could read or write, and they still have the first book they produced (it was about dinosaurs). When they were a little older, they painted an undersea paradise on the walls of the bedroom they shared at their home in Toronto. Their years at the Ontario College of Art and Design overlapped, and they spent several years cowriting screenplays (yielding several tantalizing leads but no sales).

Simon & Schuster executive art director Lizzy Bromley discovered Terry’s artwork online while searching for a cover artist for Katherine Rundell’s Rooftoppers (2014). That was Terry’s first publishing assignment; he did the interior illustrations for the book as well. Kirsten Hall, who was setting up her own agency, Catbird Productions, found Terry online not long after he’d finished working on Rooftoppers. She emailed him and asked if he was interested in representation. Terry called Eric. “That’s how I snuck in,” Eric says.

Hall asked the brothers for story ideas to pitch. They thought of a drawing they had worked on together that pictured a man on a ladder under a full moon, trimming a tree in the shape of an owl. They knew there was a story there, they just had to work it out. Hall offered it to Bromley, who leapt at the chance to work with the brothers again; she championed the book at S&S, and editor Christian Trimmer joined the team. “We were a bit out of our depth at first,” Terry says. “Everybody was so encouraging and so supportive.” The picture of the moonlight tree trimmer grew into The Night Gardener (Feb.).

The story’s hero, the topiary artist who works quiet miracles, drew inspiration from a source close to home. Terry and Eric’s father, who used to be a philosophy professor in Toronto, now lives in rural Taiwan. Even in the city he kept birds and grew trees. When Terry and Eric talk about him, the words tumble out. “He’s kind of like Dr. Dolittle,” Terry says. “He’s a beekeeper, he breeds parrots, he has peacocks, roosters, horses, dogs, all kinds of birds.” Eric adds: “He grows all his own vegetables. He’s an incredible potter.” Growing up with a father who revered all growing things gave the brothers’ story its spark.

In the first dummy Terry and Eric submitted, the entire story was a flashback, a device that reflects their screenwriting days. A boy notices a tree outside his house that is shaped vaguely like an owl, and he asks his mother about it. His mother tells him about the Night Gardener, who appeared on their street a century ago and trimmed each tree to look like an animal.

“Roughing in the dummy was the informative part,” Eric says. “You realize, wow, we really don’t have that many pages. When you’re running out of space you have go to back and rethink.” He and Terry simplified the story, moving back in time and concentrating on William, an orphan who befriends the Night Gardener. “That bought us a lot of pages,” Eric notes. The rest of the project went smoothly. “Our editors said it was as if we’d been doing this for years,” he adds.

For the brothers, collaboration is a joint effort from beginning to end, even the artwork. One brother—sometimes Terry, sometimes Eric—drafts an image and digitizes it, and the other brother adds elements or moves them around, or adds color. Image-editing software is crucial. “With a drawing, everything is locked down,” Terry says. “But with Photoshop, when they ask for edits we can move just one thing. We can change our minds. We might want to insert just one character.”

When other artists need a fresh look at their work, they often have to walk away from it for a day or two. When one Fan brother needs a fresh look, he shows it to the other one. “We’re very honest with each other,” Terry says. “We’ll say, ‘That’s not working.’ And there’s always a suggestion about how to fix it.” They rarely argue, “although we sometimes both get frustrated about the same things,” Terry adds. “We can’t coddle each other,” Eric says. “There’s no point. And we’re not sensitive. You lose that ego, because the other person isn’t out to knock you down. You’re just trying to get to a destination.”

The brothers have been so busy illustrating (they also did the artwork for astronaut Chris Hadfield’s childhood memoir The Darkest Dark, due from Little, Brown this September) that they haven’t done much in the way of public appearances. “We did a Skype interview with a school in Texas,” Eric says. “And the kids each wrote a letter and did a drawing. That was really lovely. I was so influenced by the picture books I loved as a child that it made me feel happy to think I could have that kind of influence on kids in turn.”