Gavin Rossdale was in a reflective mood on Wednesday as his oldest son Kingston turned 15.
The Bush frontman paid a heartfelt tribute to the teenager on Instagram, alongside a beautiful photo of Kingston looking out at the sunset.
Alongside the image, the father-of-four wrote: "HAPPY BIRTHDAY KING - 15 years of life’s best journey - you are my best focus and inspiration.
VIDEO: Gwen Stefani's fiancé Blake Shelton talks being a stepfather
"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."
Gavin went on to reflect on being a single parent, adding: "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_."
Gavin Rossdale paid a heartfelt tribute to his son Kingston on his birthday
Fans were quick to comment on the post, with one writing: "You are an amazing father and not bad on a guitar too. Happy birthday Kingston," while another wrote: "Aww, a wonderful heartfelt tribute to your son." A third added: "Such a sweet post, hope he has an amazing day."
Gavin shares Kingston, along with sons Zuma and Apollo, with ex-wife Gwen Stefani.
Gwen – who is engaged to Blake Shelton – also paid tribute to her son on her own Instagram page.
The No Doubt singer posted a picture of Kingston sporting long hair, sitting outside playing the guitar. "Happy 15th b day to my beautiful boy @kingsrossdale_ love u mom gx."
Gavin is a doting father to three sons and daughter Daisy Lowe
Former couple Gwen and Gavin were married for 14 years before their divorce was finalised in 2016. The singer is also a father to model Daisy Lowe from his previous relationship with Pearl Lowe.
In a 2017 interview with the Sun, Gavin made rare comments about his split from Gwen and admitted it was "shocking for everyone".
Kingston and his brothers with Gwen Stefani and Blake Shelton
"For me, it was about being solid [for our sons] and silent but respectful of Gwen. That's what it'll be forever," he continued. "Those days were the worst days ever. It's all a bit of a blur."
Gavin, 55, further explained: "We had 20 years together and that in itself is pretty incredible. It's a lifetime. I still think she's incredible. It was a lovely 20 years and we have three amazing children.
"There were a lot of positives, and with time they'll become more and more obvious."
Read more HELLO! US stories here
Like this story? Sign up to our newsletter to get other stories like this delivered straight to your inbox.