Gwen Stefani Celebrates Son Zuma's 15th Birthday with Rare Photos: 'We Love You More Than Anything'

Gwen Stefani shared a rare look at her second son on his special day

Gwen Stefani is looking back on the last 15 years.

The "Just a Girl" singer, 53, celebrated the second of her three sons on his birthday, sharing photos of Zuma over the years in an Instagram tribute on Monday.

"Happy 15th birthday Zuma !!! we love u more than anything 🩵🎉🎂," she captioned the photo montage.

The teen smiles in a selfie with his mom at the beginning of the video, which also includes photos of him with brothers Apollo, 9, and Kingston, 17. Stefani shares the three boys with ex-husband Gavin Rossdale, 57.

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Related: Gwen Stefani's Son Kingston Rossdale, 17, Performs at Blake Shelton's Oklahoma Bar

The No Doubt frontwoman was joined by her three sons as they celebrated Stefani's husband, Blake Shelton, at his Hollywood Walk of Fame star ceremony in May.

"I kind of stopped checking things off my list of great accomplishments in my life when I married Gwen, so this is just icing on the cake," said the Boys 'Round Here singer at the ceremony. "I love you so much, and that's the great thing that's happened along this journey."

In December, Shelton opened up about becoming a stepdad to wife Stefani's three sons. "They've taught me something about myself that I never knew: I'm more than just a country singer or a goofy guy."

Shelton continued to tell PEOPLE exclusively, "I'm someone they actually lean on, and that's not a responsibility that I ever had and not something that I ever considered even being into."

"It's a different kind of self-worth. Maybe it's the opposite of self-worth because you put yourself way down on the rung, and they move up ahead of you," noted the singer.

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