Charlize Theron shares a rare photo with her daughters, Jackson, 8, and August, 4, while celebrating her 45th birthday

adopted Jackson in 2012 and August in 2015, and while the actress has been fairly private about her children, she did reveal that Jackson is transgender.

In an interview with she said: "Yes, I thought she was a boy, too. Until she looked at me when she was three years old and said: 'I am not a boy!'"

She continued: "So there you go! I have two beautiful daughters who, just like any parent, I want to protect and I want to see thrive.

"They were born who they are and exactly where in the world both of them get to find themselves as they grow up, and who they want to be, is not for me to decide.

"My job as a parent is to celebrate them and to love them and to make sure that they have everything they need in order to be what they want to be.

"And I will do everything in my power for my kids to have that right and to be protected within that."

Charlize added: "I was taught by my mom that you have to speak up; you have to be able to know that, when this life is over, you'll have lived the truth you're comfortable with, and that nothing negative can come from that."

The Oscar winner, who once dated Sean Penn, never had kids with him while they were in a relationship from 2013 to 2015.

While the actor recently got , Charlize was .

She told Howard Stern in an interview: "What? That’s not true. No. I did not 'almost get married to Sean,' that’s such bulls**t.

"No, we dated, that was literally all we did, we dated."