Michael Douglas and Catherine Zeta-Jones are doting parents to Dylan, 24, and Carys, 21, and the former celebrated his birthday this week.
To mark the special occasion, all his family members paid tribute to him on social media, including his younger sister, who rarely posts online.
Carys took to Instagram Stories to share some never-before-seen pictures of herself and Dylan, from both recent times and from when they were young children.
One picture also focused on Dylan's lavish birthday celebrations, showing the college graduate sitting outside at a restaurant surrounded by multiple birthday cakes, including one with a giant '24' candle placed on top of it.
The siblings are incredibly close, and in another snapshot, the pair were seen smiling while sitting outside in another lavish looking restaurant. Another picture showed them lying on a bed wrapped up in towels.
While the pair have enjoyed a luxurious lifestyle, they are incredibly down-to-earth. Dylan went to Brown University and graduated in 2022, while Carys is a current student at the same college.
She has been studying there since 2022, and is studying International Relations and Film. According to her Linkedin, she is a co-president of the college's only club dedicated to raising awareness on climate change.
Dylan and Carys were raised in Bermuda during their early years before their parents moved to Irvington, Westchester County, just outside of New York City.
They grew up in a beautiful $12million home, but this year, Michael and Catherine decided to put the property on the market, now that their children have flown the nest.
"When I purchased our Irvington home, I knew our family would share many happy times here, and we have!" Catherine told the Wall Street Journal.
"Now that both our son and daughter have left the nest it seems like the right time to sell."
The 54-year-old revealed that she and her husband plan to leave New York altogether and spend more time across the pond. "Michael and I plan to spend more time in Bermuda and Europe," she added.
The couple also have a home in Wales, where Catherine grew up. Michael further expanded on their plans at the recent Atlantida Mallorca Film Festival, where he was awarded the Master of Cinema 2024 accolade, which was presented to him by Queen Letizia.
During his acceptance speech at the event, which took place in Mallorca, Michael revealed his plans to semi-retire, and to spend half a year in Spain.
He said: "It is an honor to receive this award in Mallorca, where I have been coming for 35 years and where I enjoy my time like nowhere else...
"I speak terrible Spanish, but I love this place more and more. Now I plan to stay here for six or seven months a year, although that doesn't mean I have retired. What happened is that at the end of 2022 I finished filming the series Franklin and then I didn't work. I continued resting in 2022 and was very happy. But I haven't gone, I have instructed my agent to only call me if a very special role comes up."