As a content development editor for American Girl, Mel Hammond wrote advice and activity books and developed fiction books. Now she writes full time, alongside two feline coworkers who have a variety of skills, including sitting on her keyboard and deleting entire paragraphs of text. Mel lives in Madison, Wisconsin. Brit Bennett grew up in Southern California and as a child was a fan of the American Girl character Addy. She earned her MFA in fiction at the University of Michigan. Her debut novel The Mothers was a New York Times best seller, and her second novel The Vanishing Half was a number one New York Times best seller. Jennifer Roy is six minutes older than her twin sister, and one inch shorter. In addition to the Trading Faces series written with Julia, Jennifer is the author of the award-winning historical books Yellow Star and Jars of Hope .

Julia DeVillers is six minutes younger than her twin sister, and one inch taller. She and her twin, Jennifer Roy, wrote the bestselling Trading Faces series, about twins who trade places. Another one of Julia's books was turned into the Disney Channel movie Read It and Weep .