According to femalefirst.co.uk, a source told Grazia magazine that "Angelina and Brad have spent much of the festive period discussing extending their family".
"They've been open with the children about it and they are all excited at the prospect," the source added.
The couple initially looked into adopting a child from Jordan, but the process was too difficult, so they are reportedly talking to orphanages in Ethiopia.
"They have always wanted Zahara to have a sibling who shares her African heritage. Ideally they'd like a little girl aged between two and three," the source said.
Pitt and Jolie, who are seeking advice from friend and adoption expert Jane Aronson, are building an AIDS clinic in Zahara's name in Ethiopia and are expected to pay a visit in April, when they will also meet with orphanage bosses.
"There is likely to be a visit to Ethiopia in the next few months to check on proceedings at the clinic. But they will visit orphanages at the same time. They hope to have everything in place to go ahead with the adoption around April," the source said.