Pregnant Jessie James Decker's Daughter Prayed for Baby: She Said, 'Jesus, Please Help Me Have a Brother or Sister'

Jessie James Decker's baby on the way is an answered prayer — for her daughter!

The country-pop singer and television star revealed in an exclusive sit-down with PEOPLE Now that her daughter Vivianne "Vivi" Rose, 3½, had a big part in the story behind her and Eric Decker's third child on the way.

"We knew that we possibly wanted a third [child], but I remember she pulled me aside — one of our friends had a baby, and [Vivianne] is really close with their child already, they're the same age. … His name's Henley, and Henley just had a baby sister," explains Jessie, 29.

"My son, [Eric Thomas II "Bubby"], is 2, so she doesn't remember him ever being a baby, they're 17 months apart," she says. "So she's like, 'Mommy, I want a baby sister like Ellie, I want a baby sister.' I was like, 'Well, if you really want a baby brother or sister, you have to pray to Jesus.' "

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"So every night I would hear her going, 'Jesus, please help have a brother or sister,' " Jessie recalls. "She would just pray. And then my mom, who's super Catholic, pulls out the rosary. So [Vivianne] pulled out the rosary and she's 3, going, 'I want a baby sister!' "

The couple — who star in the E! reality series Eric & Jessie: Game On — chronicled their decision to try for another child on an episode of the show. And Jessie tells PEOPLE that while she came from a larger family, Eric didn't — and she wanted him to have that experience he craved.

"I just felt and feel so fulfilled with our two I didn't really think about it — like, I'm not longing for another child," she explains. "I just feel like we've got it going on with Vivi and Bubby."

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"But I think because I came from a family of three siblings, I know what that's like, and it was great, and Eric came from a family of just him and his sister," she continues. "He wants to experience that whole big family process, so I'm not gonna take that away from him."

Lucky for Jessie, she has an amazing parenting teammate in her NFL star husband, 30. "He's an incredible dad, so if I had this bum dad who was like, 'I'm not changing a diaper,' it would never work out, but he is just as hands-on as I am," she says. "It is completely 50-50. We do everything together."

"And he picks up the slack if I've had a really exhausting day, so it's like, why not have another baby with this man?" adds Jessie, who just released her second studio album Southern Girl City Lights.

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The spouses of four years are stoked to expand their brood, but one thing the mom-to-be isn't looking forward to? Sacrificing that precious shut-eye.

"I'm one of those people that cannot function on little sleep," she admits. "My husband can have a power nap and survive. He's fine. Me? I have to have that eight [to] nine hours, or just forget about it."

As far as what she's most looking forward to, Jessie says it's breastfeeding again. "I really enjoy that … it's a special bond, and I think it's so important," she says. "I did it with both [my kids] for I feel like a long time for a working mom, seven [to] eight months with both of them, and I feel like I'm gonna try to go even longer this time."

Jessie says they already know the sex of the baby and have decided on a name, but are keeping mum for now. In fact, they waited a while even to spill the beans to their daughter.

"I knew [Vivi] would tell the world," says the soon-to-be mom of three of waiting to reveal the news. "We did a whole thing where we put balloons in a box and let the kids open it. They were really excited. … I told Vivi the name, so now she pulls up my shirt and says the name and kisses my belly."

"So I go to her school to pick her up and the teachers come out and are like, 'We heard about little so-and-so … she prays for it every day at lunch,' " Jessie shares. "The whole class knows, the teachers know, the faculty, the principal. I'm like, 'Oh my Lord, you're gonna tell everyone, girl.' "