Rumours have been rife that the couple are expecting two babies, but their publicists have repeatedly denied the claims.
However, the Daily Mail quotes a friend as saying: "Brad's been very quiet about this pregnancy so far but this was the weekend he decided to let the cat out of the bag. He's telling everybody close to him, because he is having to change his work schedule to get ready for the birth.
"They're having twins, Angelina is healthy, and he's thrilled that he's going to be a father once again."
The source claimed that the pregnancy was not planned, adding: "But they wanted more children and Brad says Angelina was very willing to have them herself."
Contrary to reports that Jolie will give birth in France, the friend said: "They want to have these children in Los Angeles or New Orleans. I don't think Brad wants to isolate himself and the family again like he did when Shiloh was born."