Brad Pitt with Knox (left) and Angelina Jolie with Vivienne
Junko Kimura/Getty; Jun Sato/WireImage
07/16/2009 AT 11:00 AM EDT
They've already been to France, Japan and New York City. So how did Brad Pitt
and Angelina Jolie
's globetrotting twins Knox and Vivienne celebrate their first birthday on July 12?
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."
For more on how the twins are growing up, pick up PEOPLE, on newsstands now