Angelina Jolie reveals two of her daughters underwent surgery recently

Angelina Jolie has revealed her two eldest daughters have both undergone surgery in the past two months.

The actress and director – who has three adopted children and three biological children with ex-husband Brad Pitt – opened up about their suffering and bravery in an essay for Time magazine to mark International Women’s Day.

Jolie, 44, revealed Shiloh, 13, has had hip surgery, while Zahara, 15, has undergone multiple operations for an undisclosed medical condition.

Read more: Angelina Jolie credits children for giving her 'strength'

The Maleficent star wrote: “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.

“They understand that going through medical challenges and fighting to survive and heal is something to be proud of.

“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.”

Jolie revealed youngest daughter Vivienne, 11, “studied the nurses with her sister, and then assisted the next time”.

While her sons, Maddox, 18, Pax, 15, and Vivienne’s twin Knox, 11, “were there for them, supportive and sweet.”

Read more: Brad Pitt shares his reaction to Jennifer Aniston reunion hysteria

In February the children’s father Brad Pitt, 56, was absent from the Bafta film awards in London, leaving co-star Margot Robbie to collect his Best Supporting Actor award for his performance in Quentin Tarantino’s Once Upon a Time in … Hollywood. It has now been speculated that Pitt’s absence was because he was supporting his daughters as they recovered from surgery.

Jolie filed for divorce from partner of 12 years Pitt back in September 2016.

Last year Maddox, broke his silence on his relationship with his father three years after their alleged altercation.

When asked if his relationship with Pitt was "over" the teenager, who is currently a student at Yonsei University in South Korea, said: "Whatever happens, happens."