Lord has two children, a son and a daughter, and was inspired by them while writing Rules. She states that the character of David is loosely based on her autistic son, while the character of Catherine is a mixture of herself and her daughter, who loves to draw. Most of the characters and incidents come from a very personal place in Lord's life, including the character of Jason, who was very loosely inspired by an experience she had as a kid while watching a child in a wheelchair communicating with his mother.
The Q&A following the end of the book welcomes the reader with these words, when asked where the idea for Rules came from: "I have two children, a daughter and a son, and my son has autism. One day when my daughter was about ten years old, she asked me, "Mom, how come I never see families like mine in books and on TV?" I didn't know how to answer her, so I went looking for children's books that included characters with severe special needs. I did find some, but most of the books I read seemed very sad to me. Sadness is part of living with someone with a severe disability, but it's only one part. It can also be funny, inspiring, heartwarming, disappointing, frustrating—everything that it is to love anyone and to live in any family."