When Jane Drake and Ann Love speak at children’s events, they often ask the kids to raise their hands if they have a sister. Many hands pop in the air. Then they ask who would like to spend their life working with their sister. “A lot of the hands go down,” says Love, chuckling.

The sister team Drake and Love, though, have been writing children’s non-fiction and activity books together for two decades. Their 27th book, Alien Invaders: Species That Threaten Our World, will appear this April. The book looks at the damaging ecological impact of plants and animals introduced into foreign ecosystems.

The two authors point to their own childhood as the spark for their interest in both writing and the environment. They share memories of family vacations spent on natural pursuits. “Instead of going to Disney World, we went to Yosemite National Park,” says Love, at 60 the elder sister by seven years. “We didn’t go to the Calgary Stampede, we went to the Lake Louise sewage lagoon.” Both laugh as Drake recalls one summer spent looking for “the elusive dipper,” a bird found in parts of western North America.

The two first worked together in 1988, on what was supposed to be a small pamphlet for the World Wildlife Fund. That project expanded into a book, requiring Drake and Love and their children – they each have three – to spend a lot of time together. While they worked on it, the two authors created games and activities to entertain the kids, and when the WWF book was done, they put together The Kids Cottage Book, the first title in their most enduring series. (They’ve since written five more activity books, providing information and entertainment about campfires, winter games, stargazing, and other family activities.) They also created a series of eight scrapbooks for kids to fill up with stuff about friends or family members. Though Love has written two novels on her own, Taking Control and Grizzly Dance (the latter for adult readers), the two have continually worked together.

Over the years, working sessions have often been blended with family visits; usually Drake brings her family from Toronto to Love’s home north of the city. Often a new project comes out of experiences in writing the previous title: while working on Cool Woods, they became fascinated with the snowy environment of the boreal forest, which led to their next book, Snow Amazing. Occasionally, inspiration comes from unlikely sources: Love says the 1954 film Creature from the Black Lagoon helped focus their ideas for the format and illustrations in Alien Invaders.

After research, they take time to mull over ideas and form a plan. The writing begins when the sisters together create a very detailed outline, often 20 pages long, and then divide the work based on personal interest. By the time the book is complete, though, each draft has passed through each author’s hands numerous times, a process that ensures that the final product is a blend of both their voices.

Occasionally, their different styles collide, but the sisters say that even these clashes have positive outcomes. “We complement one another,” says Drake. “I kind of get more excited and might tend to go off on a tangent, and so she kind of reins me in and keeps me very, very focused. But Ann tends to sometimes be a little bit too serious, a little bit too academic…. and so I cut to the chase with that and say, ‘Let’s see if we can make this a little more accessible.’” Both say their close bond allows them to critique each other’s work without hurting any feelings.

When asked what they would be doing without each other, each sister says she would probably still be writing. But, says Love, not working together is something “I’ve never thought about.”