Pitt and Jolie (in Malibu Oct. 30 with Maddox and Zahara) don't have to wed to adopt, but "legally, they are announcing a long-term commitment," says USC Law School associate dean Scott Altman. Photo by: FLYNET
Happy Father's Day| Angelina Jolie, Brad Pitt
Along the way, Maddox has taken to calling him Daddy, and Jolie, say friends, has never been happier. By bringing together Pitt, Maddox and Zahara, "she is creating something," says a source, "that she has never had herself."

That would be an old-fashioned nuclear family. After in-depth discussions in recent weeks, the couple decided to begin the adoption proceedings. "They are taking this," says a source, "very seriously." Says Pitt's brother Doug: "He'll be a natural."

First, however, he'll have to navigate some red tape. But once the Jolie-Pitts are officially a foursome, the clan will likely grow.

Jolie told PEOPLE in October that she's "planning" to adopt more children. "There's something about making a choice, waking up and traveling somewhere and finding your family," she said. "Sooner or later, I'll end up everywhere." And now she'll be traveling with Zahara and Maddox's dad by her side.