Michael Douglas and his 'birthday sister' Catherine Zeta-Jones celebrate their special day

Catherine Zeta-Jones and Michael Douglas are celebrating their birthdays today, September 25. Michael is now 80, and Catherine is 55, and it's the 23rd birthday they've shared since saying "I do" in 2000.

They each dedicated posts to each other on social media, with the Chicago star sharing an old photo of them from 25 years in 1999. "Happy Birthday to Michael and to me!! This was us on our birthday 25 years ago! I love you with all my heart ♥️, our friend @jeanpigozzi snapped us in New York!!" She explained in the caption.

Catherine also shared a photo of Michael on her Instagram story dedicated to him.

The birthday man shared a photo of his wife, letting her take the spotlight writing in the caption, "To my birthday sister, I love you with all my heart! May your new year be the best!" Although he had confused commenters about why she referred to Catherine as his sister, it was all fun. His wife wrote in the comments, "Thank you, sweetheart!!!"

Michael's son Cameron's sweet dedications

Michaels's son Cameron who he shares with his ex-wife Diandra Luker celebrated their birthday by dedicating posts to each of them. "I am going to jump out there and say, you Dad, may be one of the greatest men this planet has seen; or certainly of that ilk. You have made your mark for the betterment of this world and continue to do so," he wrote.

The actor shared an older photo of his stepmom writing, "So beautiful inside and out a continuous source of light and inspiration in my Life. In short; thank you for being you! Happy Birthday Catherine ♥ I Love You."