The actress unveiled her candid side as she spoke to The Wall Street Journal magazine for their April 2016 issue.
The starlet discussed her 18-month relationship with the actor – and their subsequent breakup last June.
“We were very, very new in a relationship,” the 40-year-old quipped.
“There was an understanding that I was a single mum with a very young boy who I had to put in a situation where he understood that Mummy dates but that he does not have a father, you know what I mean?”
“You have to be very careful and very honest about that stuff,” she explained. “And Sean was great with all of that.”
Following their break up, Charlize was criticised for reportedly “ghosting” her former beau, in other terms dropping out of his life with no explanation.
“When you leave a relationship there has to be some f–ing crazy story or some crazy drama. And the f–ing ghosting thing, like literally, I still don’t even know what it is,” the mum-of-two said of the claims.
“It’s just its own beast. We were in a relationship and then it didn’t work anymore. And we both decided to separate. That’s it.”
The South African native and Sean went public with their relationship in December 2013 and were instantly inseparable.
The following year it was reported that pair were secretly engaged.
During their relationship, Charlize became close with Sean’s 24-year-old daughter, model-actress Dylan Penn and the two still keep in touch.
And The Huntsman: Winter’s War actress admitted that her ex got close to her son, Jackson, now four.
“In my honesty about wanting to have more kids, there was an understanding that a relationship had to go somewhere before it was going to be – what you hope for, which ultimately did not happen,” Charlize admitted.
Indeed the actress went on to adopt daughter August Theron shortly after her break-up with Sean.
“I couldn’t foresee that, but that stuff takes time and I think it’s my responsibility as a mother to protect my child from that. And we had a very clear understanding,” she added.
During their relationship Sean previously told Esquire UK that his past marriages to Madonna and Robin Wright were discounted in comparison to his bond with Charlize and he wouldn’t rule out tying the knot a third time.
“You say I’ve been married twice before, but I’ve been married under circumstances where I was less informed than I am today,” the 55-year-old mused.
Meanwhile the notoriously private starlet shed a few tears during the uncharacteristically honest interview.
Taking it into her stride, Charlize laughed about sharing too much information.
“My publicist’s going to kill me; I’m already saying too much!”
You can read Charlize’s full interview here