Kirk Douglas' daughter-in-law Catherine Zeta-Jones reacts to his death

Catherine Zeta-Jones is in mourning.

The "Chicago" star, 50, lost her father-in-law, Hollywood legend Kirk Douglas, on Wednesday when he died at the age of 103.

Zeta-Jones took to Instagram to share a message of love for her late family member.

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An error occurred while retrieving the Instagram post. It might have been deleted.

"To my darling Kirk, I shall love you for the rest of my life," wrote the actress in the caption. "I miss you already. Sleep tight..."

In the black-and-white photo, Zeta-Jones plants a kiss on Douglas' cheek.

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The actress has been married to Michael Douglas, his son, since 2000.

In December, Zeta-Jones shared a birthday message to Douglas on Instagram as well.

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"This guy on my knee, is 103!!!!!" she wrote in the caption. "Happy Birthday Pappy!!! I love you with all my heart."

Michael, 75, also an actor, shared the news of his father's passing on Instagram on Wednesday.

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"It is with tremendous sadness that my brothers and I announce that Kirk Douglas left us today at the age of 103," Michael wrote on the platform. "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."

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"But to me and my brothers Joel and Peter he was simply Dad, to Catherine, a wonderful father-in-law, to his grandchildren and great grandchild their loving grandfather, and to his wife Anne, a wonderful husband," he continued. "Kirk's life was well lived, and he leaves a legacy in film that will endure for generations to come, and a history as a renowned philanthropist who worked to aid the public and bring peace to the planet."

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The post concluded: "Let me end with the words I told him on his last birthday and which will always remain true. Dad- I love you so much and I am so proud to be your son."