‘The idea was so infectious it consumed us both immediately. We couldn’t stop brainstorming, and before long, we started to write…’ Author Catherine Doyle tells Culture about her winning collaboration with her sister-in-law Katherine Webber on fantasy novels Twin Crowns and its newly-published sequel.
Not many people can say they’ve written a book with their best friend or their sister-in-law but happily, Katie (Webber) and I (Doyle) are lucky enough to say we have done both. First, with Twin Crowns, our fantasy-based romantic comedy about twin sisters separated at birth, and again with the sequel Cursed Crowns, which follows our twins, Rose and Wren, as they attempt the hard task of ruling a fractured kingdom together.
Although we’re now sisters-in-law, when we first met ten years ago, Katie and I were both budding authors of children’s books, just starting out in our careers. Back then, I didn’t even know Katie had a brother (and now I’m married to him!). Despite our fast friendship and shared passion for all things YA fantasy, it never occurred to Katie and me to ever sit down and write a book together. For one thing, co-writing a 100,000+ word tome presents its own logistical challenges, and for another, we each had our own projects on the go. Children’s books to write and deadlines to meet.

And then, one day in 2020, we found ourselves stuck in the middle of the pandemic, much like everyone else. My wedding to Katie’s brother, Jack, was temporarily on hold and by a stroke of luck (or perhaps fate), Katie and I were both in between deadlines. We were also both looking for something to lift our spirits.
It was around this time that Katie called me up with an idea: a book about twins separated at birth. One, a witch. The other, a princess. The story of their switch would play out as a romantic comedy, with laugh-out moments and swoony love interests that would sweep us off our feet. We would set in a wild and beautiful kingdom inspired by ancient Ireland, with magic knitted into its bones and enchanting myths that began in the stars. There would be witches and princesses, backstabbing and betrayal, and at the heart of it all – two sisters coming to know each other for the very first time.
When you co-author a book about sisterhood with your sister-in-law, the journey is all the more rewarding.
The idea was so infectious it consumed us both immediately. We couldn’t stop brainstorming, and before long, we started to write. Family phone-calls slipped seamlessly into conversations about castles and royalty, the characters in our stories sometimes feeling as real to us as our own partners! We’d often text each other at 2am with the spark of a new idea. Once, Katie called me up with a premise that was so funny I spat out my coffee.
Although we each write from a separate points-of-view (Katie writes Princess Rose, while I write Wren the witch), we planned every chapter together, making sure we knew exactly what was happening to each sister and when. However, there was always a little room to add in a little surprise, like a stolen library kiss or a flirtatious moment in a hot desert spring. One of the most enjoyable things about co-authoring is getting to write half the book and experience the other half of it just like a giddy reader.
And best of all, when you co-author a book about sisterhood with your sister-in-law, the journey is all the more rewarding. Not only are we immensely proud of these books, but we’re proud of each other, too.
Cursed Crowns is published by Farshore (Harper Collins)