Jeremiah Brent tells PEOPLE his children with husband Nate Berkus - Oskar, 10 weeks, and Poppy, 3 - "have very different energies"

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Jeremiah Brent and Nate Berkus‘ 3-year-old daughter Poppy is taking to her role as a big sister like a duck to water, but even she has her limits.

The interior-design pro spouses chatted with PEOPLE recently about their new partnership with Huggies to introduce a line of customizable, monogrammable and highly giftable diapers called Huggies Made By You, as well as their new dynamic as a family of four since welcoming son Oskar Michael via surrogate on March 26.

“She’s been great,” Brent, 33, says of Poppy’s attitude toward her baby brother. “She’s super sweet and nurturing. It’s nice to have a feminine energy in the house other than my own.”

He calls Poppy “a strong girl,” adding of the siblings’ personalities, “They have very different energies. He’s a big mush and she’s a very independent woman. So it’s been fun and sobering to raise a young strong woman [and] make sure that you don’t get in her way when you don’t need to be.”

Jokes Berkus, “She kind of checks in with him first thing in the morning, gives him a kiss and then proceeds to ignore him for the rest of the day.”

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Credit: Christopher Dibble Photography

Jeremiah Brent and Nate Berkus with daughter Poppy and son Oskar

Huggies Launches Huggies Made By You
Credit: Astrid Stawiarz/Getty

Nate Berkus and Jeremiah Brent with son Oskar and daughter Poppy

Ever the protective sister even when she’s doing her own thing, Poppy still runs into Oskar’s room whenever he cries. “She wants to make sure that someone is on it,” says Brent. “And changing his diaper. She loves the ceremony of going in for a diaper change.”

The proud dad explains that Poppy is “actually super patient” as opposed to jealous of her new sibling, and “likes to have her alone time” — as opposed to baby Oskar, whom Berkus describes as more “needy” than their daughter was as a newborn.

“It sounds bad, but he’s the type of kid who likes to snuggle,” Brent clarifies. “He likes to be held a lot. Our daughter was very independent the second she came out. She was fine to be alone. Our son likes to be held and snuggled. Which is great, because I can’t get enough snuggles.”

Credit: Ashley Burns Photography

Jeremiah Brent and Nate Berkus with daughter Poppy and son Oskar

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Berkus, 46, calls the differences between his children like he sees them. “I think it’s fair to say, I think everybody knows at this point, girls are just smarter than boys,” says the Nate & Jeremiah by Design star. “So it might be early to call that with our two children.”

He adds, “But I think that is not going to change within the Berkus-Brent household. It’s time they took over the world. Poppy is like this, and has been since before she was able to talk — she’s been definitive, knows exactly what she wants.”