Alaia, 27, shared the news Friday via Instagram in a photo of birthday boy Aronow kissing her baby bump, captioning the flick, “I made something extra special for @andrewaronow’s birthday this year….. #BABYARONOW coming to ya August 2020 #👶🏻👶🏻👶🏻 #🎀🎀🎀it’s a girl🎀 🎀🎀 #happybirthday and #yourewelcome.”

Hailey, 23, immediately jumped into the comment section to share in their joy, writing, “My niece” and “Screaming!!!!” before sharing the photo to her own Instagram Story.

“I’m gonna be an Aunty!!!!!!!” she captioned the pic. 

The model told Vogue Arabia in 2018 that while she’s looking forward to parenthood, she and husband Justin Bieber are in no hurry.

“I love kids and I can’t wait to have my own. I would say that now, that’s a closer reality, but definitely not anytime soon.”

Bieber agrees, telling Zane Lowe shortly after his second wedding to Baldwin, “I want to start my own family in due time. I want to enjoy being married for a little bit, go on tour, be married, enjoy traveling with just us, build more of our relationship. I think that it’s definitely the next step, for sure.”