There isn’t a day when Michael Douglas and his wife, Catherine Zeta-Jones, don’t think about the actor’s late father, Kirk Douglas. The Basic Instinct star and the Mask of Zorro actress paid tribute to the Spartacus alum in honor of what would’ve been his 104th birthday.

“Happy Birthday, Dad!” Michael, 76, wrote alongside a homemade video of throwback photos on Wednesday, December 9. “I miss you and thank you for always giving the best advice! Love, Michael.”

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Catherine, 51, also shared a touching post for her beloved father-in-law. “Missing you every day,” the Entrapment star sweetly penned next to a snap of Kirk giving her a kiss on the cheek. “Happy birthday, Pappy.”

This year marks the first birthday since Kirk’s death at age 103 in February 2020. At the time, Michael announced the iconic Paths of Glory actor died in a heartbreaking post on social media.

“It is with tremendous sadness that my brothers and I announce that Kirk Douglas left us today at the age of 103,” the Kominsky Method actor wrote on behalf of his siblings, Joel Douglas, 73, Peter Douglas, 65, and late brother Eric Douglas. “To the world, he was a legend, an actor from the golden age of movies who lived well into his golden years, a humanitarian whose commitment to justice and the causes he believed in set a standard for all of us to aspire to.”

Michael learned a lot from his dad over the years, including how to be a good father to his three kids, Cameron Douglas, 41, Dylan Douglas, 20, and Carys Douglas, 17, as well as how to pave a legendary career in Hollywood.

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“I think his stamina and tenacity are the qualities that stand out for me,” the Academy Award once exclusively told Closer Weekly. “He has taught me to always give it your best shot at whatever you take on.”

Michael noted it takes a certain person to make it to 100 years old, let alone 103. Looking back on his famous father’s decades-long career, the Fatal Attraction alum praised Kirk for paving a memorable run in showbiz.

“It is all about quality, not quantity. 100 years old is certainly a milestone, but the facts are what Dad has accomplished in his 100 years,” Michael shared. “His 90 plus movies as a star and producer; the eleven books he’s written and published since he turned 70; the tremendous amount of public service to his country and faith.”

Because of Kirk’s unwavering dedication to his family and work, Michael revealed the most important lesson his dad instilled in him. “Never give up,” he gushed to Closer. “Just keep working out. That’s what he [said]. Keep working out.”