Duff was born in Houston, Texas on September 28, 1987.[5] She is the second child of Susan Colleen (née Cobb), a homemaker, and Robert Erhard Duff, a partner in a chain of convenience stores. She has an elder sister, Haylie Duff, who is also an actress/singer. After Duff's mother encouraged Duff to take an acting class alongside her elder sister, Haylie, both girls won parts in various local theater productions. At the ages of eight and six, respectively, the Duff sisters participated in the ballet, The Nutcracker Suite with Columbus BalletMet in San Antonio.[5] The siblings became more enthusiastic about the idea of acting professionally, and eventually relocated to California with their mother. Duff's father stayed at the family home in Houston to take care of their business.[6] After several years of auditions and meetings, the Duff sisters were cast in various television commercials.