Gwen Stefani and Gavin Rossdale Celebrate Son Kingston's 18th Birthday: 'My First Born Baby Boy'

Gwen Stefani’s son Kingston Rossdale is now an adult!

The No Doubt frontwoman’s eldest child, whom she shares with ex-husband Gavin Rossdale, turned 18 on Sunday, May 26, and the singer celebrated his birthday with a sweet tribute.

To mark one of motherhood’s biggest milestones, Stefani, 54, put together an Instagram post documenting Kingston’s life from early childhood to now, including several pictures of the mother-son duo throughout the years.

She kicked off the compilation with an adorable video of a young Kingston telling the camera that he has a crystal ball. “It tells the future,” he says while rubbing his eyes, before adding matter-of-factly: “It’s really hard to find.”

Then, fittingly set to UB40’s song “Kingston Town,” Stefani shared lots of baby pics of Kingston, including a photo of him drooling and another of him rocking a tank top that says “Lil Lamb” in the singer’s signature 2000s style.

The PEOPLE Puzzler crossword is here! How quickly can you solve it? Play now!

The “Simple Kind of Life” rocker also shared photos of the then-toddler joining her in her dressing room, and a clip of Kingston taking after his musically inclined parents by strumming a guitar.

In one particularly sweet clip, the now-18-year-old holds his brother Zuma Rossdale, whom Stefani and Rossdale, 58, welcomed two years after Kingston in 2008.

The “Sweet Escape” singer finished Kingston's birthday tribute with more recent pics, including several with her husband, Blake Shelton.

“Happiest of birthdays Kingston,” she wrote in the caption. “My first born baby boy :) cannot believe u are 18 today… i love u!”

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer​​, from juicy celebrity news to compelling human interest stories. 

Rossdale also celebrated his son's new adulthood with an Instagram post, which he filled with photos of the teen, including a shot with both of his brothers, Zuma, 15, and Apollo, 10.

“HAPPY BIRTHDAY KINGSTON,” the Bush frontman wrote in the caption. “18 today and a massive step into your future. so far the best ride of my life and I can’t wait to see where you go from here. I have total belief in you and deeply admire the man within.”

Nodding to Kingston’s choice to continue in both his and Stefani’s musical footsteps, he continued: “You have grace, charm and humility. You are at the wheel of your destiny so choose wisely. Your musical talent is nuts and soon the world will hear your heart sing. Follow your muse, stay curious and keep creating.”

"I could not love you more than I do. I wish you all the happiness all the health and all the creativity. Love you dad,” he finished.

Responding in the comments, Kingston wrote, "Best dad ever" and “I love you so much!”