Brad Pitt with Knox (left) and Angelina Jolie with Vivienne
Junko Kimura/Getty; Jun Sato/WireImage
They stayed home – in Los Angeles, where their parents threw a family birthday party. Older siblings Maddox, 7, Pax, 5, Zahara, 4, and Shiloh, 3, all helped bake two cakes: one for Knox, one for Viv.
Grandparents Bill and Jane Pitt also flew in from their hometown of Springfield, Mo., for the low-key bash.
When it comes to raising six kids, "It is chaos," Jolie told PEOPLE last year, "but we are managing it and having a wonderful time."
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