Hilaria Baldwin always knew she wanted to be a mother — she didn’t know, however, what that would look like for her family.
“I never knew how many kids I wanted to have,” Hilaria, 33, tells PEOPLE exclusively in this week’s issue. “I didn’t know how much I’d like it. And I really, really like it.”
The fitness guru and husband Alec Baldwin, whom she wed in 2012, welcomed their first child together, daughter Carmen Gabriela, in August 2013. Less than two years later, the couple’s son Rafael Thomas joined the family and in September 2016, son Leonardo Ángel Charles was born.
Want all the latest pregnancy and birth announcements, plus celebrity mom blogs? Click here to get those and more in the PEOPLE Babies newsletter.
RELATED VIDEO: Baby on the Way for Alec and Hilaria Baldwin
With three kids under four at the time, the busy parents thought their family was complete. But after welcoming their youngest, Hilaria says she and Alec began thinking about another baby and ultimately decided to take a different approach to getting pregnant.
“We were like, ‘Oh, should we have another kid?’ ” she says. “We were like, ‘You know what? Let’s try something different — let’s try.’ [With] the other ones, it’s not like we were like, ‘Oh my God, how did this happen?’ But this is the only one we [planned].”
Now Hilaria is pregnant with the couple’s fourth baby — and third son! — due in the spring. “We’re really excited,” she says of their upcoming addition.
Equally excited? Daughter Carmen, who was told she was going to be a big sister again only days before Hilaria and Alec announced the news on social media.
“She was like, ‘I can’t wait to tell everybody at school!’ We’re walking out the door and she’s like, ‘There’s a baby in my mommy’s tummy!’ I’m like, ‘Stop it! Not yet! We’re not telling yet!’ ” Hilaria says, laughing.
“That’s the reason I didn’t tell her before, because everybody would have known,” she explains.
FROM PEN: Former Bachelorette Ashley Hebert Rosenbaum Opens Up About Her Sibling Rivalry Fears
Although Carmen is thrilled to soon 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,’ ” Hilaria shares. “She’s like, ‘No, you don’t understand, Mommy. It’s going to be a girl.’ I was like, ‘No, I promise. I promise you it’s a boy.’ “
Despite already having a sister — Alec is also dad to daughter Ireland, 22 — Carmen is set on another little girl joining the family. “She is committed to a fifth child,” says Hilaria.
For Alec, 59, and the fourth-time mom-to-be, another baby isn’t completely out of the question.
“People are like, ‘Oh, they must be Catholic’ or ‘Oh, she must just want all of his money.’ I’m like, ‘If I wanted all of his money, why am I having so many children? Children are expensive!’ ” she jokes. “Seeing how much my daughter would like to have a sister, do we try for that? I have no idea.”
She adds, “I’ve had so many [kids] because I really like them and we have such fun times. I’m going to have four kids in a little over four years and it’s just one of those things where I’m going to let life lead me in that direction.”
For more about Alec and Hilaria Baldwin’s life at home with three (almost four!) kids under 5, pick up the latest issue of PEOPLE, on newsstands Friday.