Why Charlize Theron Knew She Would Adopt Her Kids: 'It Was Always My First Choice'

Charlize Theron tells PEOPLE for this week's issue why she always wanted to adopt her children

Of all the parts Charlize Theron has played throughout her successful career — a super-spy, a one-armed warrior and a mom suffering from postpartum depression in her new movie Tully (out May 4), to name a few — the Oscar winner says the role that makes her the happiest these days is the one she plays for an audience of two.

“My kids make me laugh like nobody’s business,” the actress, 42, tells PEOPLE for this week’s issue of being mom to August, 2½, and Jackson, 6.

She adds, “I’m kind of going through it right now because my little one is potty training, so night time, we’re up three times a night changing sheets and pajamas and things like that, but I wouldn’t change it for anything.”

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Charlize Theron and son Jackson

Watch the full episode of People Features: Charlize Theron: Fame, Family and Finding Happiness, streaming now on PeopleTV.com, or download the PeopleTV app on your favorite device.

Theron, who adopted Jackson in 2012 and August three years later, says she always saw adoption as her pathway to motherhood, due in large part to her upbringing in South Africa and early exposure to orphanages and children in need in her community.

“Even when I was in relationships, I was always honest with my partners, that adoption was how my family would look one day,” she says. “This was definitely not a second option for me. It was always my first.”

For much more on Charlize Theron and her new movie Tully (out May 4), pick up the latest issue of PEOPLE, on newsstands Friday.

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Theron, an only child, also reveals that she always knew she wanted more than one kid, even if that meant dealing with sibling rivalry.

“We went through this really beautiful stage a year ago where the baby was hugging her sibling and there was all this love and affection,” she says. “I was bawling my eyes out every day saying, ‘This is the most beautiful love I have ever witnessed in my life.’ ”

Continues the star, “Now the baby is almost 3 and realizes she doesn’t have to do everything her sibling tells her. There’s a lot of wars in my house. I’m like, ‘Where’s the cute period that we went through?’ ”

Tully opens in theaters May 4.