Paul McCartney is one of the most famous musicians in the world, but when it comes to his family life he's notoriously private.MORE: Paul McCartney and wife Nancy Shevell enjoy romantic trip to the beachHowever, the Beatles star delighted fans after announcing some exciting news involving two of his daughters, Mary and Stella McCartney.The award-winning music star is teaming together with Mary, Stella, and food brand Linda McCartney, to launch a vegan cookbook. VIDEO: Paul McCartney shares