MADDOX IS TURNING 23!

Brad and Angelina's children are preparing to fete their eldest brother, Maddox, when he turns 23 on Aug. 5. "

He can't wait to celebrate with his mom and siblings," shares a source. "Angie's made plans at one of his favorite restaurants.

All the kids are excited about getting together." Brad won't be there: Maddox - who's studied at South Korea's Yonsei University and worked as a producer on his mother's movie First They Killed My Father, which is set in his native Cambodia "still wants nothing to do with his father," the source confirms.

U.S.," shares the source. "He's been working on his speech and has already warned Brad it's going to be a bit controversial, but mostly just hilariousHe's infamous for his pranks." They're in no rush to hear what George has in store, though. Brad and Ines "have felt married for a while now," explains the source.