Catherine Zeta-Jones farewells her father-in-law Kirk Douglas: 'I miss you already'

Catherine Zeta-Jones has shared a touching tribute to her father-in-law Kirk Douglas, following his death on Thursday. He was 103.

The actress was close to the veteran star and they bonded immediately after she married his son, actor Michael Douglas, in 2000. 

"To my darling Kirk, I shall love you for the rest of my life. I miss you already. Sleep tight," she wrote on Instagram, alongside a photo of the pair sharing a tender moment.

Zeta-Jones has always been close to her father-in-law, with the actress often sharing sweet photos of the pair on Instagram.

In December, she shared a photo of the pair embracing to mark his 103rd birthday. 

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

And last September, as she and Michael celebrated their respective 50th and 75th birthdays — the couple have the same September 25 birth date — she also shared an intimate snap taken with Kirk.

"Last night dinner with Pappy," Catherine captioned a photo of them holding hands during the joint celebration. 

When Catherine and Michael married almost 20 years ago, many eyebrows were raised because of the 25-year age gap between them.

Despite the judgement they received from others, one person remained firmly in their corner: Kirk.

On the couple's 19th wedding anniversary in November last year, Catherine shared a sweet note Kirk had given them to mark the milestone occasion.

"Dear Michael and Catherine, Happy anniversary!" read the note typed on Kirk's personal stationery.

"Michael, you have learned a very important lesson, to stay married you must obey your wife! Keep practicing what I do with my wife."

After splitting from Michael's mother, Diana Douglas, in 1951, Kirk went on to marry Anne Buydens in 1954. They remained married for 66 years up until his death.