With the spookiest day of the year fast approaching, the actress took to Instagram to share an old photo of her two children, Carys, 13, and son Dylan, 16, along with their grandfather Kirk Douglas, the legendary Hollywood actor.
Catherine's children with their grandfather Kirk Douglas
"A Halloween throwback!! How adorable was my father-in-law Kirk Douglas dressed as a clown with Carys as Alice in Wonderland and Dylan as a Titanic survivor? #TBT," wrote Catherine, 47.
The snap showed the youngsters and their grandfather on top form as they embraced the Halloween spirit in their fancy dress.
While some of the actress' fans commented on her nonagenarian father-in-law – "Oh, my God! He is 99 years! Great!" wrote one fan – others noted the similarities between Catherine and her brood.
"That little girl is her mother's TWIN!!" one fan posted, while another replied: "Dylan, takes after Catherine (breathtaking beautiful)."
Dylan and Carys are 16 and 13 respectively
Catherine and her husband Michael Douglas, who is 25 years her senior, will celebrate their 16th wedding anniversary in a couple of weeks.
Despite their brief period of time living apart, the couple are now happier than ever and have spent the past year travelling the world. Catherine and Michael even went back to Aspen, Colorado where the Behind the Candelabra actor popped the question on New Year's Eve in 1999.
Speaking to People, Michael, 72, said: "To have the kids there – we went to the house where I was. They let us in and everything else. I showed them where the chair was and they were like, 'Ew, this is gross!'"