Fox, 26, who is currently pregnant with the couple's first child, said she knew he was the one for her despite their 12-year age gap, reported Femalefirst.
"The first time I saw him I got butterflies. The first time he casually touched me, there was so much electricity. I truly feel like he's my soulmate. We're destined to live this part of our lives together," she said.
The Hollywood star, who married Green in 2010 in Hawaii following a brief split, also says being a stepmother to his 10-year-old son Kassius makes her extremely happy.
"A lot of things make me happy. But I feel unbelievably happy when my stepson tells me I'm beautiful. When I started living with Brian, his son was only two and I was 18.
"I've been looking after Kassius since he was three - it's part of my world that very few people really ever understood about me. I love being a stepmom and the experience grounds me when nothing makes sense in my life," she added.
