Brad Pitt and Angelina Jolie want to adopt another child.

The couple - who currently have biological kids Shiloh, five, and three-year-old twins Knox and Vivienne and adopted trio Maddox, 10, Pax, seven, and six-year-old Zahara - reportedly promised their adopted daughter they would take on the care of another youngster from Ethiopia, the poverty-stricken African nation where she was born.

A source said: "They are really excited about it. Brad and Angie made a promise to Zahara years ago that they would adopt another child from the region so she could have a sibling to relate to."

The couple are also said to believe having seven kids will bring them more "luck and happiness".

The source added to the Daily Star newspaper: "Also, seven has always been Brad's lucky number. He and Angelina think it would bring them luck and happiness."

Brad has previously admitted he always wanted to raise a large family.

He has said: "I know it seems extreme from the outside, but I've always kind of operated this way. When I know, I know, and why mess around?

"I had a friend who had a big family when I was a kid. I just loved the chaos around the breakfast table and the fighting and the ribbing, and the mom making pancakes for everyone or the dad making pancakes. And I just decided then if I was ever going to do it - this left some indelible mark on me - if I was ever going to do it, that's the way I was going to do it."