Billy Bob Thornton is "proud" of the way his ex-wife Angelina Jolie handles her life.

The 56-year-old actor - who was married to Angelina from 2000 to 2003 - is impressed with how the actress, who has six children with Brad Pitt, deals with her hectic lifestyle and believes she and Brad are perfect for each other.

"We're great friends and always will be. I'm proud of the way she's handled having a family. She's great for Brad, Brad's great for her. I support them 100 per cent. Angie is a little girl and a woman and a teenager and a ghost all wrapped up in one," he said, writing in his book The Billy Bob Tapes: A Cave Full of Ghosts.

Proving how close they are, Angelina wrote the foreword in the book, describing the director as a funny guy but similar to a "mad mathematician."

"He has an unmatchable wit and can make you laugh until your face hurts. To be with him is like being with a mad mathematician. He is constantly counting and repeating. Some people walk through life able to quiet the voices in their heads. He can't. And I, and everyone else who knows him well, we love him for it," she wrote.