Angelina Jolie and Brad Pitt were so shocked to find out they were expecting twins, they burst out laughing.The Hollywood superstars welcomed Knox Leon and Vivienne Marcheline in Nice, France last month.And the pair admit they couldn't believe the news when they first found out Jolie was carrying twins, as they weren't expecting to add two more tots to their bustling brood.Jolie says, "We were in shock and could not stop laughing."Pitt adds, "We burst into hysterics. My sister had made a joke about twins literally the night before, because my grandparents and sis both had twins. Angie was on the table during the sonogram, and we were in hysterics. We didn't see this one coming." The actor also says he was emotionally moved as he cut the babies' umbilical cords at the birth, adding: "I felt an awe words fail to describe."