Judith Viorst was born and brought up in New Jersey and now lives in Washington, DC. Her books include the beloved Alexander and the Terrible, Horrible, No Good, Very Bad Day, and its many companion books; adult fiction and nonfiction including the New York Times bestseller, Necessary Losses; poetry for children and adults, and four musicals.

Her most recent book of poetry for children, What Are You Glad About? What Are You Mad About? was published in 2016. Lulu Is Getting a Sister is the fourth book in the Lulu series.

Sophie Blackall has illustrated several children's books and has also animated for TV. Her books include Meet Wild Boars by Meg Rosoff, and Ruby's Wish.

Of Red Butterfly, she says, "It was such a delight to delve into ancient China. From the moment I first read this story, my mind has been dancing with red butterflies and peach blossoms, lotus pools and autumn moons, princesses and secrets." Sophie lives in New York, USA.