Jack Black let the news slip while doing a joint-interview with Jolie in Cannes to promote their movie, Kung Fu Panda. "You're gonna have as many as [the] Brady Bunch when you have these," he said during the chat with Today show's Natalie Morales.
Asked by Morales if she is indeed having twins, Jolie replied, "Yeah, yeah, we've confirmed that already. Well, Jack's just confirmed it actually."
The children will be the fifth and sixth for the Jolie and Pitt. The family currently consists of Maddox, 6; Pax, 4; Zahara, 3; and Shiloh, who turns 2 this month.
Pressed about the gender of the babies, Jolie said, "We would like to keep that private."
Pitt and Jolie are "thrilled" about adding to their brood, a source close to the couple told PEOPLE after Jolie debuted her baby bump at the Independent Spirit Awards in February.
The Jolie-Pitt clan have been staying in France at Microsoft co-founder Paul Allen's historic Florentine-styled Villa Maryland. Jolie is currently at the Cannes Film Festival promoting Kung Fu Panda.
Excerpts of the interview will air Wednesday on Access Hollywood, and the full interview will air Thursday on the Today show.