But there they were over the weekend looking anything but tiny tykes as the two siblings stepped out for a bite to eat with a bodyguard in Woodland Hills, Calif, on Saturday.
In fact, given his height, Maddox actually looked quite a bit older than 11 while strolling alongside his 9-year-old brother.
Maddox sported a WWZ tee, likely a nod to dad's upcoming World War Z flick. Pax, meanwhile, rocked an iconic Nirvana shirt.
Yep. They grow up so fast!