LOS ANGELES (DM): They may be one of the most famous families in the world. But when it comes to birthdays Brad Pitt and Angelina Jolie celebrate just like any normal family. The two super stars were seen taking their twins Knox and Vivienne ice skating for their seventh birthday in Los Angeles on Sunday. It was a family affair as the entire brood were present for the celebration on ice. Brad, 51, was seen leading his son Knox to their waiting car as the two both wore black. But little Knox appeared to be advertising one of his dad’s favourite bands as he sported a Metallica shirt, while Brad was dudded in a button down and jeans.