Actor George Clooney has cast doubt on rumours his close pal Brad Pitt is to become a father again, insisting he has no knowledge of Angelina Jolie's alleged pregnancy. Late last year (07), the Tomb Raider actress spoke of her and partner Pitt's plans to have more children to add to their brood of four, telling America's In Touch Weekly magazine, "Who knows, maybe we will have another child in 2008." And her comments have sparked speculation over whether she is with child - but Clooney, who is best friends with his Ocean's 13 co-star, admits he is none the wiser. He tells Usmagazine.com, "I have no idea. I don't think so. I haven't heard anything." Pitt and Jolie have three adopted kids - Maddox, six; Pax, three, and Zahara, two - and their biological child, 20-month-old Shiloh.