Katherine Schwarzenegger Pratt is the bestselling author of three self-help books as well as a picture book about her rescue and adoption of her dog, Maverick. She serves as an Ambassador for Best Friends Animal Society and the ASPCA, and she also hosts the weekly Instagram Live series BDA Baby. Her newest children’s book, Good Night, Sister, illustrated by Lucy Fleming, focuses on the special, supportive bond shared between two sisters—one seemingly brave, and one not-so-much—as they navigate a change in their bedtime routine. We spoke with Schwarzenegger Pratt on the eve of her book launch and national tour about how she approached this project as a sister, and now, also a mother of sisters [Pratt shares two young daughters with her husband, actor Chris Pratt].

What sparked the idea for your latest book?

I knew that after doing my last book, I wanted to do a children’s book next. I was pregnant with my first daughter, Lyla, and I was trying to figure out what it was exactly that I was going to write about, or if that was even going to work out. Then, when Lyla was born, I was reading to her a lot in the evening, right from the beginning. I would sit with her in the rocking chair and read a lot of the same books that I read growing up and I found myself having so many flashbacks of my childhood, all these memories of my siblings and I reading. I wanted to write a book really celebrating the relationship that I had with my sister, Christina, growing up. We’re so close in age and we did pretty much everything together, and we still do today as adults. I wanted to write something as a tribute to the closeness of our relationship, and also the dynamic that we had growing up: I was much more shy and reserved, and Christina was the bolder and braver one out of the two of us and did everything first. I leaned on her a huge amount to be the brave one. I started writing the book right after I had my daughter Lyla and I finished it right before I got pregnant with my second daughter [Eloise], so, it worked out very well.

What was your collaboration with Lucy Fleming like?

When I was writing the book, and also when I finished the manuscript, I had visualized and made a lot of very specific notes about what I had imagined the illustrations to be like. Whether it’s the decor in the rooms, or the blankets on the bed, or just the way the two girls look—they were very intentionally created to look a lot like Christina and I did as kids. And all the stuffed animals in the book were based on the exact stuffed animals that my daughter Lyla was gravitating towards and had around her when she was really little and they’re still in her crib today. To be able to go back and forth with Lucy, someone who is so talented, and who also really enjoyed the process and took my notes into consideration, was really awesome.

Also, I will say that being able to now do a children’s book as a mom, I had much more insight than when I did it the last time. Since I’ve been reading so many books with both of my girls, I have a better understanding of what they naturally gravitate towards in illustration. In the book, a lot of the colors, the expressions on the girls’ faces, and the design of things came from my having a good audience—a two-and-a-half-year-old and an eight-month-old—to base those images off of.

Did you have a favorite stuffed animal growing up? Do you still have it?

I had a favorite stuffed animal unicorn, and I actually still do have it—it’s either at my mom’s house or my dad’s house, but I definitely have it. I went pretty much everywhere with that unicorn. I was a big stuffed animal fan when I was younger; they all had names and very specific purposes. And it’s wild now, with my two-and-a-half-year-old, she’ll sometimes wake up in the middle of a nap, or before she goes to sleep at night, she’ll do a full roll call of all the stuffed animals that are in her crib. It’s really sweet to see. You know, kids and their stuffies are definitely a big thing, so being able to create a book where these stuffies have special powers that allow kids to feel comfort and confidence is really important.

Do you have any other book projects in the works?

Yes, I’ll do another one for sure. When I look at my books or just projects in general that I work on, they’re really based on life experience. And I think, especially as a mom now, I see how important reading to children from the very beginning is in their development and just in life. The routine of sitting and reading to your children encourages stillness in this fast-paced world we live in. I love being able to contribute to that tradition and hopefully write things that become a part of people’s bedtime routine and are a staple in their at-home library. I feel really lucky to be able to write books and I hope to continue to do it.

I’m excited to see how this book is received. I’ve given it to a couple of my daughter Lyla’s friends who are her age; they all are really excited about it. And I have a couple of my girlfriends calling me saying their daughters are now asking for sisters, which is not the goal of the book, necessarily. But I’m thrilled that little kids are excited about the relationship between sisters and also knowing that if you don’t have a sister that you’re able to find that relationship and that bond in a friend or a cousin or a parent. Being able to really nurture that kind of relationship from an early stage can help kids feel comforted knowing that they have somebody to turn to when they need that little cuddle to get them through a scary time. That’s the goal of the book—to celebrate those kinds of bonds, whether it’s in sisterhood or friendship.

Good Night, Sister by Katherine Schwarzenegger Pratt, illus. by Lucy Fleming. Penguin Workshop, $18.99 Feb. 7 ISBN 978-0-593-38581-4