Fans Can't Believe How Grown-Up Gwen Stefani's 15-Year-Old Son Is in Birthday Photos

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Gwen Stefani's son Zuma is growing up!

The newly-minted 15-year-old boy is the middle child of his famous family, born in between the "Luxurious" singer and ex-husband Gavin Rossdale's other two sons: Kingston, 17, and Apollo, 9.

On Monday, August 21, The Voice judge took to Instagram with a celebratory montage video, showcasing a collection of rare snapshots of her growing kiddo.

Several childhood pictures of Zuma were displayed in the clip—which was set to the tune of "Something in the Orange" by Zach Bryan—including multiple mother-son shots and even one with his stepdad, Stefani's current husband and country crooner, Blake Shelton.

"happy 15th birthday Zuma !!! we love u more than anything 🩵🎉🎂," the upload was captioned.

In the comment section of the social media post, fans couldn't believe how much he has grown.

"Wow I cant believe Zumba [sic] is 15 already @gwenstefani ! 😮I remember when he was first born! Boy how time flies!" one fan said, before adding, "Hope you have the most amazing Birthday ever with your friends and with your beautiful family Zuma!!! ❤️❤️❤️🎂🎉🎊🎁."

Another assumably joked about their own age, wondering, "How can he be 15 when I am still 23?"

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"Can’t believe how grownup he’s become, such a handsome big boy and very like mummy x 💙," a third agreed.

An additional user chimed in with, "Happy Birthday Zuma.. You’re extra special being the middle child.. May all your dreams come true.. 🎂🎉🎈🥳🎊🎁."

Several more kept it simple by sending in classic well wishes for the birthday boy.

Happy 15th spin around the sun, Zuma!

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