David Cassidy, best known as the well-coiffed heartthrob who starred in the 1970s series "The Partridge Family," watched his family members succumb one by one to dementia.

First, his grandfather slowly lost his mind to the disease.

Then his mother, the Broadway and television actress Evelyn Ward who Cassidy once said "basically raised me for years on her own," was diagnosed with Alzheimer's around 2002. Eight years later, Cassidy said she "can't walk, can't talk and lives in a nappy."

In 2012, Ward died at 89 years old "after suffering from Alzheimer's-related dementia," according to the Hollywood Reporter.

"In the end, the only way I knew she recognized me is with one single tear that would drop from her eye every time I walked into the room," Cassidy told People. "I feared I would end up that way."

Just before Ward's death, Cassidy became an advocate for those with Alzheimer's, speaking at nationwide engagements for Alzheimer's and dementia organizations and shooting public service announcements.

"People don't really want to talk about it, but we need to, which is why I'm going to be speaking publicly about it," Cassidy told the Daily Mail.

Now, one of Cassidy's biggest fears has come to fruition. In an interview with People magazine published on Monday, he announced that at 66 years old, he is suffering from dementia.

"I was in denial, but a part of me always knew this was coming," Cassidy told People.

At the end of 2017, Cassidy, who has spent the past several years touring the world and playing solo songs alongside tunes from "The Partridge Family," has decided to quit playing live shows to focus on his health.

"I want to focus on what I am, who I am and how I've been without any distractions," he told People. "I want to love. I want to enjoy life."

As he wrote on his website:

"I will always be eternally grateful for the love and support you've shown me. I still love very much to play and perform live. But it's much more difficult for me now.

"I'm not going to vanish or disappear forever. I'll be able to communicate much more through my website and my Facebook page. As you can imagine this has been truthfully THE MOST DIFFICULT DECISION I HAVE EVER MADE IN MY ENTIRE LIFE.

"I'm eternally grateful to each and every single one of you.

I'm going to play live, everywhere around North America, through 2017. I hope you will find a way to come and be part of my celebration!"

The revelation comes after a disastrous weekend show in Agoura Hills, Calif., during which Cassidy couldn't remember the lyrics to many of his older songs. In videos from the show obtained by TMZ, Cassidy appears to slur his words and falls off the stage. He attributed the problems to his burgeoning dementia.

Sadly for the former teen idol, this is the latest in a string of life's unfortunate curveballs.

The child star has spent much of his middle age battling alcoholism, much like his father, actor Jack Cassidy. From 2010 to 2014, he was arrested three times for driving while intoxicated. The final two arrests came within six months of each other, finally leading him to rehab in South Florida.

A month after this last arrest, his third wife Sue Shifrin-Cassidy filed for divorce, according to TMZ. In an interview with Piers Morgan, Cassidy attributed the divorce in some part to his drinking.

"If I take another drink, I'm going to die, physically, mentally, emotionally, spiritually. I'm dead . . . It's very humbling and it's also humiliating," he told Morgan, before adding that admitting to his disease gave him some hope.