According to Lara, her sons Rocket, 4, and Racer, 2, have known about their new baby brother from the get-go.
"We talk about it a lot because I have spent a lot of time in bed recently. And they're like, 'What are you doing?'
"All boys, I think, want a brother. So another brother… you know, it's building the football team. They're excited!"
Lara shares her sons with her husband, actor Sam Worthington, and the couple have been living in Los Angeles for several years.
Rumours Lara and her actor hubby— who's busy filming the four follow up films to 2009's Avatar— were expecting another bundle of joy began swirling in August after a source revealed details to The Daily Telegraph.
"It's early days but she's very excited. Lara is pregnant with her third child," they told the publication.
The makeup company founder has opened up about her husband in the past, revealing the hunky Hollywood star is an incredible dad to their little ones.
"He is a fantastic father, fantastic husband and we’re just a really good team.
"We’ve grown together and grown as a family and I think that’s the most important thing. "We travel everywhere together and we never have more than two weeks apart from each other — and that really works for us.
"He’s just so good with the kids, he does the night feeds and everything — he is seriously superhuman," she said.