Douglas posted a sweet photo of him kissing his father on the head on Instagram Sunday as he expressed his appreciation for the host of tributes to the acting great in the wake of his death.
"Thank you so much for your kind and thoughtful words,'' he wrote. "Our family is so grateful for your support and we send our love to everyone!"
Douglas' wife, Catherine Zeta-Jones, also posted a photo of Michael and Kirk together on Instagram in echoing her husband's sentiments about her father-in-law.
"Michael joins me in thanking you all for your overwhelming love, kind words and prayers since the passing of my father in law Kirk,'' she wrote. "My whole family appreciated every word. Love to you all."
Kirk Douglas was also honored at Sunday night's Academy Awards as part of the annual "In Memoriam" segment honoring Hollywood greats who have died in the past year. He was a three-time Oscar nominee who also received a Lifetime Achievement Award in 1996.
Two-time Oscar winner Tom Hanks also paid tribute to Douglas during Sunday's ceremony with a reference to "Spartacus," one of Douglas' most iconic roles, when speaking about the Academy of Motion Picture Arts and Sciences’ new museum opening in Los Angeles in December.
“It’ll be a very big deal, we’ll see you there, and I am Spartacus!” Hanks said.
It was the latest in a series of appreciations of Douglas, including a moving tribute posted by Michael Douglas following his father's death on Feb. 5 in which he highlighted Kirk's loving nature.
"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," he wrote on Instagram. "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."
Zeta-Jones also posted a touching photo of herself with Kirk following his death.
"To my darling Kirk, I shall love you for the rest of my life. I miss you already,'' she wrote. "Sleep tight..."
The tight bond between Michael and Kirk was highlighted in 2018 when Michael became emotional as he joined his father in getting a star on the Hollywood Walk of Fame as a 101-year-old Kirk joined him at the ceremony.
"It means so much to me, Dad, that you're here today," he said. "I thank you for your advice, for your inspiration, and I'll say it simply and with all my heart: I'm so proud to be your son."