Brad Pitt and Angelina Jolie's decision to add a child from Vietnam to their family has been a long time coming.
For months the couple have been preparing to find a sibling for Maddox, 5, Zahara, 2, and 10-month-old Shiloh, a "process that began shortly after Shiloh was born [in May]," a source tells PEOPLE in its new issue.
It wasn't until March 2 that a Vietnamese official revealed
that Jolie, 31, had filed preliminary papers to adopt a child – according to one adoption worker, "a boy between the ages of 3 and 5."
(Vu Duc Long, the head of the country's international adoption department, told the Associated Press on Wednesday that the boy is between the ages of 3 and 4 and from the Tam Binh orphanage on the outskirts of Ho Chi Minh City.)
But the source close to Jolie says there are still a few more steps before welcoming a new family member. "It's wonderful that people are excited about it," says the friend. "But she is only at the beginning of a very comprehensive and detailed process."
Why Vietnam? Jolie has traveled extensively in Southeast Asia and has visited the country at least twice. After adopting Maddox from Cambodia and Zahara from Ethiopia, she mused to Good Morning America
in December that it might be a good idea to "balance the races so there's another African person in the house for Z [and] another Asian person in the house for Mad."
As they navigate adoption red tape, the family of five has been happily settled in New Orleans since January, where Pitt, 43, has been filming the romance The Curious Case of Benjamin Button
Locals frequently spot them strolling through the French Quarter, buying baby clothes (a "Dirty South" T-shirt for Maddox, a black dress for Zahara and a hot-pink onesie for Shiloh) and dining out with Button
costar Cate Blanchett.
Soon they'll return home to L.A., where Pitt will resume filming. Jolie, meanwhile, continues to speak out about the atrocities in Darfur as she awaits the phone call that will enable her to officially add to her brood. The good news can't come soon enough. "I just want more kids," she told PEOPLE recently. "I'm having a great time."
For more on this story, including details on Brad and Angelina's visit to the orphanage and Angelina's mission to Darfur, pick up this week's
PEOPLE, on newsstands Friday.