Olivia Wilde's son Otis is "hard" on his younger sister Daisy.
The 33-year-old actress has revealed her three-year-old child is like a "drill sergeant" to his eight-month-old sibling, and is already acting like the protective older brother because he puts her though a baby "boot camp".
Speaking about her brood - who she has with her partner Jason Sudeikis - on 'The Late Show with Stephen Colbert' on Tuesday (13.06.17), the brunette beauty said: "He's like a drill sergeant. I don't know who let him watch 'Full Metal Jacket', but he is so hard on her. He's really putting her through the works, it's boot camp. So she's going to come out of it really ripped and with a great attitude. But he screams!"
And when the two youngsters battle it out Olivia has revealed Otis will scream harsh words at her to claim his territory.
She continued: "'You don't live here!' is what he screams at her."
But Olivia thinks the reason for Otis' outburst is because he doesn't want to "share" his mother with anyone, not even his sibling, and because he misses his mother when she is busy working.
She said: "I think he's aware that he's sharing me with her because I'm on Broadway and as everyone who's in a play will tell you, you miss a lot of bedtimes and it's tough."
However, the 'House' star has revealed her upbringing was much different because her sister Chloe Cockburn, 38, was "so nice" to her when they were children.
Olivia said: "I have an older sister who was so nice to me, so I'm not familiar with this."
And the star has revealed she was also "nice" to her 24-year-old brother Charlie.
She explained: "But I have a little brother and I was nice to him. So I don't know."