One member of Hilaria Baldwin and husband Alec's family is really gunning for a baby sister, the fitness expert explained on Friday's Today show

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Hilaria Baldwin isn’t closing the door on more little ones.

During a Friday appearance on the Today show, the 34-year-old fitness expert and mother of four demonstrates some of her favorite yoga poses to fellow moms Hoda Kotb and Jenna Bush Hager, and dishes on whether she and husband Alec will be adding more children to their household in the future.

“I have a daughter and then I have three boys,” says Hilaria, whose children are Romeo Alejandro David, 10 weeks, Leonardo Ángel Charles, 22 months, Rafael Thomas, 3, and Carmen Gabriela, 5 next month. “And my daughter is very sure that she is going to have a sister.”

“She does have a sister — she has Ireland, and Ireland is so wonderful and they have a great relationship,” she adds of Alec’s 22-year-old model daughter from his previous relationship with Kim Basinger. “But there’s something about a little sister that she really wants.”

“I think it’s possible. Not [for sure],” Hilaria admits, replying when Kotb asks whether her husband is on board, “Alec thinks it’s very possible. He comes from a big family.”

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Credit: Hilaria Baldwin/Instagram

Hilaria and Alec Baldwin with their three oldest children

Hilaria’s secret to parenting four kids under the age of 5 is “managing every single moment of the day,” she shares, explaining that she co-sleeps with Romeo and bathes her kids “morning and night” every day.

“It’s very fast — I’m so efficient,” The Living Clearly Methodauthor says of the cleanup process.

As for keeping her relationship with Alec, 60, healthy, Hilaria reveals, “When the babies are sleeping, we always spend time together. … We just like each other. We’re very different — we’re extraordinarily different, the complete yin and yang, but we like each other.”

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Although Carmen was thrilled to have a baby in the house again, learning that she would be getting another brother took a bit longer to get used to.

“She was a little bit disappointed. [She said,] ‘How about you have a girl first, then you can have another boy?’ I was like, ‘It doesn’t work that way! I don’t get to choose,’ ” a then-pregnant Hilaria told PEOPLE in November.

“She’s like, ‘No, you don’t understand, Mommy. It’s going to be a girl,’ ” she recalled. “I was like, ‘No, I promise. I promise you it’s a boy.’ She is committed to a fifth child.”