The couple - whose two-year-old adopted daughter Zahara is from Ethiopia - are hoping to visit African orphanages over the Easter holidays in March to find another daughter.
Angelina's brother James Haven revealed: "They are creating one big family and will keep adopting as long as they are able to."
The couple - who have three adopted children, Cambodian boy Maddox, six, Vietnam-born Pax, four, Zahara and 20-month-old biological daughter Shiloh - have vowed to reduce their hectic work schedules so they can accommodate another child.
James is quoted by Britain's Daily Mirror newspaper: "Angie and Brad talk about how much they have been taught by their kids. In many respects Angie saved Zahara's life and there are so many more children whose lives she could save and she talks about that constantly."
Angelina, 32, has previously spoken of her desire to have a "balanced" multi-cultural family.
She said last year: "Should you balance the races, so there's another African person in the house for Zahara, after another Asian person in the house for Mad? We think so. "Shiloh has Brad and me to look at."