Charlize Theron's children have a "beautiful" bond.

Charlize Theron

Charlize Theron

The 40-year-old actress loves watching the interaction between four-year-old Jackson and her baby daughter August.

She said: "I was an only child, and to watch that sibling relationship I feel like I'm watching something so sacred and beautiful. Like, he walks into a room and he doesn't even look at her and she just lights up and I'm, like, in front of her going crazy trying to get a reaction... It's so beautiful."

The 'Huntsman: Winter's War' star - who adopted August as an infant last year - can't believe how quickly her little girl is growing up.

Speaking to 'Extra', she said: "She's great, she's growing like a weed. It's, like, insane - it's unbelievable how quickly they become little people. I'm trying to hang on to my little baby, but she's just fighting right through that like, 'I'm ready to go.' "

Charlize - who has been single since splitting from Sean Penn last year - has grown to "value" different types of love as she has gotten older.

She said: "I think that the older I've become, the more I've valued and realised there's so many different kinds of love. When we're young... young girls, we just think of the romantic kind. When you become a parent, the love you have for your children and you have a sisterhood around you, that love that you have from your girlfriends... there's so many different kinds of love."