Hard to believe this is only half their family!

Brad Pitt and Angelina Jolie arrived in Tokyo on Sunday with three of the couple's six children -- waving to fans with son Pax and 5-year-old twins Knox and Vivienne.

The twins, who celebrated their birthday earlier this month, are getting so big ... though not big enough that they don't still need their blankies.

Not only did the family travel to Japan for yet another "World War Z" premiere, but Angie also hosted a screening of her movie "In the Land of Blood and Honey" at United Nations University.

No word yet on why Shiloh, Maddox and Zahara didn't make the trip too.

See more photos in the gallery above. And our personal favorite below -- how cute is Viv?!