"Every marriage has priorities and they have been able to navigate them up until now," the source said. "Brad has different priorities. He's a leading actor with movies coming out. She has her things she wants to do and no one is saying that’s wrong."
"Her global ambitions are part of the current problem -- I don't think anyone wants their kids all over the place," the source added.
The Allied star wants to resolve his and Jolie's issues "amicably and privately," and hopes to see his six children soon, according to the source. Pitt is currently in Los Angeles, the source adds, but keeping a low profile.
"He's being careful," the source said. "He's leaning on friends for support. This isn't a happy time for anyone."
Meanwhile, Jolie is being advised by her closest female friends, Lady Arminka Helic and Chloe Dalton, another source tells ET. According to the source close to the Pitt-Jolie situation, the two women have been "fueling the actress' aggressive approach against Pitt" from the beginning.
"Angelina is very close to Arminka and Chloe, and really has left her Hollywood circle in recent years to focus on politics and human rights," the source said, adding that the actress first met Helic through her UN work a few years ago. "Angelina respects the two of them completely and doesn't make any decisions without them."
Jolie has asked for physical custody of their children in her divorce filing -- 15-year-old Maddox, 10-year-old Shiloh, 12-year-old Pax, 11-year-old Zahara, and 8-year-old twins Vivienne and Knox. Our source tells ET, however, that Pitt wants to be with his kids and have some custody.
Find out more about Jolie's influential friends in the video below: