By Agence France-Presse
"It is with great sadness that myself and my family announce the unexpected passing of our son and brother, Chris Cattrall," she said in a tweet, less than 24 hours after publicly appealing for help in finding him.
"At this time we ask for privacy. We want to thank you all on social media for your outpouring of love and support in this trying time," she said without specifying the cause of death.
Her younger sibling disappeared from his home in Canada's Alberta province for five days.
"MISSING! This is my brother Christopher Cattrall or Chris as we call him," she wrote in an Instagram post that accompanied a picture of the 55-year-old, sporting a short haircut, a slight smile, and a black sports-style jersey.
She added that he had not been seen since January 30, and that he left his keys, cell phone, and wallet on the table of his home in the town of Lacombe, while the front door was unlocked.
"This is not like Chris. He... would never leave his unlocked home without those items nor his seven beloved dogs," she wrote.
"Chris is 55 years old, six feet tall (1.83 meters), 200 pounds (90 kilograms), blue eyes, short brown hair, goatee, average build and usually wearing a waist length hooded winter coat with black gloves, blue jeans and calf high black winter boots," she added.
The Royal Canadian Mounted Police had also issued an alert on Sunday. CBC television cited the police as saying Chris Cattrall's death was not considered suspicious.