In an essay written for Time magazine for International Women's Day, the actress revealed that two of the six kids she shares with ex Brad Pitt recently had surgery.
"I have spent the last two months in and out of surgeries with my eldest daughter, and days ago watched her younger sister go under the knife for a hip surgery," she wrote. "They know that I am writing this, because I respect their privacy and we discussed it together and they encouraged me to write. They understand that going through medical challenges and fighting to survive and heal is something to be proud of."
While Jolie didn't mention any specific names in the article, only referring to Zahara as her eldest daughter, ET has learned that Zahara, 15, and Shiloh, 13, were the two kids who underwent surgery. Jolie and Pitt are also parents to Maddox, 18, Pax, 16, and 11-year-old twins Knox and Vivienne.
"I have watched my daughters care for one another. My youngest daughter studied the nurses with her sister, and then assisted the next time," Jolie shared. "I saw how all my girls so easily stopped everything and put each other first, and felt the joy of being of service to those they love."
"I also watched them face their fears with a resolute bravery. We all know that moment when no one else can help us, and all we can do is close our eyes and breathe. When only we can take the next step or breathe through the pain, so we steady ourselves and do it," she continued. "Their brothers were there for them, supportive and sweet. But on this International Women’s Day, writing from the hospital, I find myself focusing on my daughters for a moment, and all that I have learned from them and other young girls I have met around the world."
ET has learned that the two surgeries Jolie and Pitt's daughters underwent are completely unrelated to one another. A source also tells ET that Jolie thanks everyone for their concerns and support. ET will not further speculate about a child's health.
Back in November, Jolie revealed to Harper's Bazaar that her and Pitt's children have "been through a lot" in recent years.
"The part of us that is free, wild, open, curious can get shut down by life. By pain or by harm. My children know my true self, and they have helped me to find it again and to embrace it," she said at the time. "They have been through a lot. I learn from their strength. As parents, we encourage our kids to embrace all that they are, and all that they know in their hearts to be right, and they look back at us and want the same for us."
"I am conscious every day that I have... the ability to encourage my children to explore the world, including the world of ideas and expression, without there being limits to what they are allowed to study or know or imagine themselves doing in the future," she added. "I want the children to grow up in the world -- not just learning about it but living it and having friends around the world."
"My body has been through a lot over the past decade, particularly the past four years, and I have both the visible and invisible scars to show for it," she told Harper's Bazaar. "The invisible ones are harder to wrestle with. Life takes many turns. Sometimes you get hurt, you see those you love in pain, and you can’t be as free and open as your spirit desires. It’s not new or old, but I do feel the blood returning to my body."
"Knowing our true self is a very important question for all of us. Especially a child," she continued. "I think kids need to be able to say, 'Here's who I am, and what I believe.' We can’t prevent them from experiencing pain, heartache, physical pain, and loss. But we can teach them to live better through it."