In a sweet Instagram post, Catherine Zeta-Jones paid tribute to her beloved father-in-law Kirk Douglas on December 9 for his milestone 101st birthday. Along with a fun photo of the pair, the 48-year-old actress dedicated a special message to the legendary actor, who is the father of her movie star husband, Michael Douglas. The Oscar-winner lovingly wrote on social media: "101 today!!!! My darling Pappy on my knee. Happy Birthday to my wonderful, inspirational and loving father in law, Kirk. Love you with all my heart. ❤️#hero."

Catherine Zeta-Jones shared a fun photo of father-in-law Kirk Douglas on her lap Photo: Instagram/ Catherine Zeta-Jones

If Kirk's birthday is anything like the last, he will undoubtedly celebrate in serious style. He marked his 100th birthday last year in true Hollywood fashion. The former actor's A-list family and famous friends gathered at the gorgeous Beverly Hills Hotel in honor of the special day, including his son, Michael and daughter-in-law Catherine. His children were joined by their children: Dylan, 16 and Carys, 13. Some other notable attendees for the happy occasion were: Steven Spielberg, Arthur Cohn and Jeffrey Katzenberg, who is the CEO of DreamWorks Animation.

MORE: Michael Douglas reveals how he knew Catherine Zeta-Jones was 'the one'

Catherine is known to posts photos of her father-in-law on her social media pages, showing the close relationship they share. The mom-of-two recently shared a pic of herself and Kirk at the L.A. Mission Legacy of Vision Gala back in November. She wrote: "Last night was an amazing and memorable night, where I was honoured with the Anne Douglas Award at the Vision of Legacy Gala. So lovely to be with our family for such an important evening on behalf of the Los Angeles Mission! #lamission."

MORE: Catherine Zeta-Jones shares cheeky throwback photo of her as a baby

Kirk's incredble career began when he won a scholarship to the American Academy of Dramatic Acts, where Lauren Bacall was a fellow student. Within a decade Kirk had earned three Oscar nominations, for Champion (1949), The Bad and the Beautiful (1952) and Lust for Life (1956). He has donated millions to charity, with the last known donation being $15 million to a center for Alzheimer’s patients in honor of his 99th birthday.

More about