Katherine Schwarzenegger Pratt knew she wanted to write a children's book about sisterhood almost immediately after she gave birth to her daughter, Lyla.
"I just found myself sitting in the rocking chair with her at night, reading all of these books that I read when I was younger," Schwarzenegger Pratt, 33, tells TODAY.com. "I just had all these flashbacks — so many memories of reading when I was little. It was this crazy, emotional experience that I was so unprepared for as a new mom."
The mom of two says that because so many of those memories included her younger sister, Christina, she wanted to pay "tribute" to the siblings' special dynamic.
"We're so close in age — we did everything together — so I wanted to write a children's book that was celebrating the relationship between sisters," she adds.
Now, with a 2-year-old and an 8-month-old in tow, Schwarzenegger Pratt is the proud author of the children's book, "Good Night, Sister" — an ode to the bond between sisters, though you don't have to have a sister or even a sibling to connect with the book's message.
"My brother Patrick posted about my book last night, and he's like: 'I'm unclear why this isn't called 'Good Night, Brother," Schwarzenegger Pratt says, laughing. "OK, relax Patrick."
The oldest of four, Schwarzenegger Pratt says she is extremely close with all of her siblings: Her sister most of all. The pair FaceTime nearly every morning and text at least 10 times a day.
"It's a problem," she says.
Schwarzenegger Pratt adds that her relationship with her sister certainly informs the way she raises her daughters, who are 16 months apart. Despite their young ages, Schwarzenegger Pratt says she's very intentional about the language she uses in order to establish a foundation that will help her daughters create and maintain a close bond.
... the bond they have with a sibling that close in age means they have a built in playmate and, later in life, a built in best friend.
Katherine Schwarzenegger Pratt
"Just based off of how Christina and I were raised by my mom, so much (of my upbringing) was done really gently and lovingly and not comparing the two (of us)," she explains. "It's about allowing kids to be celebrated for their own individual interests, separate from each other, while allowing kids to also understand that the bond they have with a sibling that close in age means they have a built-in playmate and, later in life, a built-in best friend."
Combating sibling rivalry or feelings of jealousy are also top of mind for Schwarzenegger Pratt, who says that when she was pregnant with her youngest, Eloise, she considered "the language that you use with your first child" in order to not have any "bad feelings or negative feelings towards the next child."
"Never using the second child as an excuse not to do something with the first child," she adds, as an example. "I've definitely been very interested in making sure that I'm prepared, language wise, to be mindful with my words and my actions and to always allow them to feel equally loved, equally supported and individually, uniquely their own people."
While Schwarzenegger Pratt is less than two years older than her sister, she is eight years older than her youngest brother, Christopher.
"I have very vivid memories of when he came from from the hospital, taking care of him when he was little, packing his diaper bag and laying out his outfit," she explains. "He was my first real baby doll come to life. It's such a special relationship."
Schwarzenegger Pratt already sees that relationship blossoming between her daughters and their brother, Jack, whom her husband, Chris Pratt, shares with his ex-wife, Anna Faris.
"It's been really beautiful to see my stepson step into this role of big brother with both of my girls, and to be able to see my girls really just love to play with their big brother," Schwarzenegger Pratt says. "I think they have enough of an age different where they get along so easily now. And now that Lyla is getting older, she's really fun to play with and I think (Jack) sees that now. It's really cool to be able to watch their little relationships blossom as they get older."
Schwarzenegger Pratt also wants that "older sibling" relationship for her daughters, adding that she certainly wants "as many kids as we're able to have."
"I'm from a big family so I love the idea of having a big family ourselves," she adds. "My two girls have each other and they also have their brother — both my husband and I would love to keep going."