The couple are also parents to daughter Carys
On Tuesday, both actors posted in celebration of son Dylan's 23rd birthday.
"Happy birthday Dylan! May YOUR new year, bring you joy, imagination, and love," the proud dad, 78, wrote, signing the post, "Your biggest fan, Dad."
The Mask of Zorro actress, 53, commented, "Happy birthday my boy❤️."
In her own tribute, Zeta-Jones — who also shares daughter Carys, 20, with her husband — shared a photo of her and Dylan when he was an infant. "23 years ago today, my boy @dylan__douglas was born," she wrote.
"He is the gift that keeps on giving, over and over and over and over again. I love you my love♥️."
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The Ant-Man star also shares son Cameron, 44, with his ex-wife Diandra Luker.
In April, Douglas and Zeta-Jones celebrated Carys' 20th birthday by posting heartfelt tributes on social media. "20 years ago today my daughter Carys came in to my arms and there is not a day I haven't cherished," Zeta-Jones captioned an Instagram. "Happy birthday beautiful lady🎂♥️🎂."
Douglas also took to Instagram to wish his daughter a happy birthday. "To my darling Carys, wishing you a happy birthday! Now that you are leaving your teens, may this be a wonderful New Year for you darling! I love you, Dad," he captioned his post.
Throughout the years, Douglas' children have made appearances at several red carpet events and movie premieres. His oldest child, Cameron, even joined Douglas on screen in a few projects.
In December, Zeta-Jones told PEOPLE that her family life has just been getting better and better. "Both my daughter and Dylan have been so incredibly supportive to me, not just as an actor, but just me, you know. I'm extremely blessed to be able to have both of them in my life."
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