Hilary Duff's son Luca is being an "amazing" big brother, his actress mum praised.

The 31-year-old and musician Matthew Koma welcomed daughter Banks Violet Bair in October and in an interview with Entertainment Tonight, the mother of two shared that her six-year-old son Luca, who she shares with ex-husband Mike Comrie, is already really comfortable in his new role of big brother.

"Obviously a newborn needs their mom the most and when I start to feel bad that she consumes most of my time, I look at him and he’s totally fine," Hilary told ET. "He’s so loving towards her and is always, like, holding her face and wants to hold her.

"When she starts to cry he’s like, 'Mom, she’s gonna blow! Get her!’ It’s really sweet. It's like she’s always been there and he’s just cool.”

The Younger star also praised new dad Matthew, who she has been dating since January 2017, for being a natural with their baby daughter.

"Matt’s amazing," the actress gushed. "He’s a really good dad and he’s patient with her."

Now that her household has expanded to include two children, alongside their four dogs, Hilary admitted it's "mayhem" but she doesn't want to complain, when others have more on their plate.

"It’s insane and amazing at the same time and you just do it," she added. "You just figure out a way to do it. But I don’t know if we call it balance yet. It’s mayhem."