The apple doesn't fall far from the tree.
Rossdale -- who also shares younger sons Zuma and Apollo with Stefani -- took to Instagram on Wednesday to celebrate Kingston's big day.
"HAPPY BIRTHDAY KING - 15 years of life’s best journey," he wrote. "You are my best focus and inspiration-you are smart funny and kind with oceans of empathy-to me that’s all you need to make your mark -i could not be more proud of you - and i love you more every day -i am in awe of you -shine on 🖤-and yes i feel a lovely responsibility (huge)with your development -shout out to all my the single parents who are love joy and survival 🖤 - my sweet boy —@kingsrossdale_."
While the first pic featured Kingston staring out over the horizon, the next photo proved heir family resemblance.
"On your marks get set. life. 🖤. @kingsrossdale_," Rossdale wrote alongside a close-up shot of his son.
Stefani also sent birthday wishes to Kingston, writing, "Happy 15th b day to my beautiful boy @kingsrossdale_ love u mom gx."
Kingston has a lot of love in his life as he gears up for another trip around the sun. In a February radio interview with KFROG's The Ride with Kimo & Heather, Blake Shelton gushed about being a soon-to-be stepfather.
"I take it very serious. But I also have a blast with it, I'm not gonna lie," he continues. "I don't take it so serious that I'm not enjoying this time because I really am, especially now that we're five years into this thing. I can't imagine my life without these kids now."
See more in the video below.