Oliver Hudson tells PEOPLE his sister Kate, who's expecting a baby girl, is "fierce" and doesn't need any parenting advice from her big brother

Oliver Hudson can’t wait to meet his new niece.

The Splitting Up Together star, 41, opened up to PEOPLE Tuesday night at the ABC and Freeform Upfronts Party, held at Tavern on the Green in N.Y.C., and admitted everyone is stoked about his pregnant sister Kate Hudson‘s baby daughter on the way.

“I was there!” he said of the bash where Kate, boyfriend Danny Fujikawa and her sons Bingham Hawn, 6½, and Ryder Russell, 14, revealed a little girl was on the way. “I had no time to react because Bing, her other kid, had a knife in his hand — he was popping the balloon and I was holding him.”

“The balloon goes boom and it’s a girl but then Bing is sort of running with a knife and I’m like, ‘Get over here!’ ” the actor recalls. “And trying to get the knife, so I had no time to actually celebrate until maybe 15 seconds later. I was super excited. We are all so happy it’s a girl!”

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Oliver and Kate Hudson

Disney ABC Upfront Presentation, Arrivals, New York, USA - 15 May 2018
Credit: Stephen Lovekin/Variety/REX/Shutterstock

Oliver Hudson

Oliver — dad to daughter Rio Laura, 4½, and sons Bodhi Hawn, 8, and Wilder Brooks, 10 — tells PEOPLE Kate, 39, is “fierce” and doesn’t need any parenting advice from her big brother.

“She loves my daughter and is with my daughter all the time,” says the former Scream Queens star. “Rio is sleeping over at my sister’s house all the time.”

“Rio looks up to her because my sister is a dancer and a performer and that’s all my girl wants to do and be,” he adds. “Auntie Kiki is what she calls her, and it’s all about Auntie Kiki. There is literally no advice I could [give] her. She’s ready.”

Kate Hudson Hong Kong Mandarin Oriental OpeningCR: Courtesy of Harry Winston
Credit: Courtesy of Harry Winston

Kate Hudson

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Kate is one of three children, with two brothers: Oliver and their half-brother Wyatt Russell. And the latter is just as over the moon for the mom-to-be as Oliver is.

“I was happy. I was teary-eyed because I know how badly she wanted a girl,” he told PEOPLE in April. “I know Danny, I’m sure in some part of every man’s brain you’re like, ‘I’d love to have a little me.’ ”

Added Russell, 31, “But when he met my brother’s little girl Rio, who’s the cutest thing in the entire world, she made him be like, ‘Okay, I want a girl.’ So they’re really excited.”