"Kim and Kanye have been incredibly involved in the surrogate process," a source tells PEOPLE

Another Kardashian girl is on her way!

A source tells PEOPLE that Kim Kardashian West and husband Kanye West are “thrilled” to be expecting a daughter, sharing, “They are so excited about their future baby girl.”

Earlier this week, multiple sources confirmed to PEOPLE that the couple’s surrogate is pregnant with their third child. The couple are already parents to son Saint, 21 months, and daughter North, who turned 4 in June.

“They can’t wait to add a new addition to their family and are just so incredibly happy,” the first source says, adding that the baby is expected to arrive in January.

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Credit: Kim Kardashian/Instagram
Credit: Dimitrios Kambouris/Getty

Back in June, PEOPLE learned that the couple had hired a surrogate to help them expand their family. The news came some time after Kardashian West was advised of the risks of carrying another child on her own due to her struggles with placenta accreta during both her previous pregnancies.

“Kim and Kanye have been incredibly involved in the surrogate process,” the source says, noting that Kardashian West has been “super adamant” in ensuring the surrogate sticks to a healthy diet.

“Kim and Kanye both want the healthiest baby possible and are making sure the surrogate is abiding by the routine they’ve set for her,” adds the source.

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But not everyone is quite as excited about the family’s incoming fifth member.

“North isn’t the most thrilled to be a big sister again,” shares the source. “She’s had the tendency to get really jealous about Saint and wants all of the attention to herself, but Kim and Kanye thinks it’s just a phase and are hoping she will grow out of it.”

Kardashian West previously opened up about North’s sibling rivalry with Saint last month while guest hosting Live with Kelly & Ryan.

“I don’t know if it’s because she’s the older sister. I don’t know what it is. I thought it was a phase. She does not like her brother and it’s so hard for me,” said the 36-year-old reality TV star, adding, “She would get so jealous when I would breastfeed and all that kind of stuff. And now, the phase isn’t going away.”