Ashton Kutcher and Mila Kunis' daughter Wyatt thinks her baby brother is "her baby".

Mila Kunis and Ashton Kutcher

Mila Kunis and Ashton Kutcher

The famous couple welcomed their son Dimitri into the world in November, and it seems their two-year-old daughter has already taken a shine to the tot as she "loves the baby so much" she's convinced he belongs to her.

Ashton, 39, said of the relationship between his two children: "Wyatt thinks the baby is her baby, and at some point I'm going to have to explain to her it's not really her baby. I don't know how I'm going to do that. She loves the baby so much.

"It's like 'Of Mice and Men'. She's like, 'I love you and hold you and squeeze you and name you George.' I'm afraid she's like Lenny, like, 'You're going to squeeze the baby's head off, honey!'"

But the 'Jobs' actor admits the love between siblings doesn't always go both ways, as little Dimitri is often "afraid" of his big sister.

He added in jest: "He loves everyone. Anyone comes near him and he's like, 'Hi!'

"But when Wyatt comes near him ... he's like Kung Fu Panda when she comes near. He's afraid she's going to kill him.

"I went through a phase where I had to keep Wyatt alive, and then I went through a phase where I had to keep her from killing herself, and now I'm going through a phase where I have to keep her from killing the other baby."

And Ashton - who tied the knot with 33-year-old Mila in 2015 - is worried his daughter might love their newest addition more than she loves her father.

Speaking on 'The Ellen Degeneres Show', the 'Cheaper By The Dozen' star said: "She loves this baby - maybe more than me. It's, like, borderline."