Hugh Hefner's youngest son says it's hard to watch his dad "struggle" in his old age.

Cooper Hefner, 25, gave an update on Hefner's health in an interview with The Hollywood Reporter following reports the 91-year-old Playboy founder is ailing.

"It's tough to watch him struggle, but I'm just happy it's physical and not mental," he told the publication.

Cooper, who became chief creative officer of Playboy in July 2016, said he regularly seeks advice from his half-sister, former Playboy chairwoman and CEO Christie Hefner, as he guides the magazine into the future.

"She can relate to the situation more than anyone could," he said of his sibling's counsel. "For me as a 25-year-old, that's sometimes challenging. My emotions get the best of me."

Hefner has largely retreated from the spotlight in recent years, leading some to believe the Playboy founder is "too sick" to leave his mansion.

His rep told Page Six in September the nonagenarian is doing "fine."

"It is no secret that over the past few years he has suffered with back pain that has made it a bit more challenging for him to get around, but at 90 years of age he is enjoying his life and still very involved in the day-to-day activities of editing the magazine," the rep said.

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Cooper shared similar sentiments about Hefner's health in an interview with E! News in April.

"He's doing fine," he said. "My dad has always made the joke that if the mansion was your house, why would you want to leave?"

"I think because he has stepped back from the day-to-day operations of the business, people have thought that his health was not very good," he added.

"The reality is he has a really bad back -- that happens when you're 90 -- and he is enjoying life at the mansion."

Hefner is also dad to 61-year-old son David Hefner and 27-year-old son Marston Hefner.

He married his third wife, model and former Playmate of the Month Crystal Harris, in December 2012.