Pippa Middleton is dating her longtime friend George Percy, heir to the duke of Northumberland, People.com said Friday. Middleton, 28, is the sister of Kate Middleton, who married Britain\'s Prince William last year. She met Percy, 27, when both were students at Edinburgh University. Percy\'s family owns Alnwick Castle, which was transformed into the Hogwarts School of Witchcraft and Wizardry in the Harry Potter film franchise. GALLERY: The Most Desirable Women of 2012 \"George is very smitten and completely in love with her,\" a source close to Pippa Middleton told The Sun newspaper in London. People.com said Middleton and Percy started dating after the Middleton family\'s New Year\'s Eve party. \"Pippa sat herself next to George at supper and made sure she was hanging off his arm all night,\" an insider told the Sun. \"And then she made her move.\"