 Another central plot line of the books is Mia's relationship with Michael Moscovitz, Lilly's older brother.Their relationship survives obstacles throughout several books of the series, such as their age difference and Mia's (often overwrought) anxieties, as Mia works out how to effectively manage romantic relationships as a maturing adolescent.In Disney's "The Princess Diaries" 2001, Mia, who was portrayed by Anne Hathaway is aged 16, has a license to drive, and owns a 1965 Mustang.