(CNN) David Cassidy, who came to fame as a '70s teen heartthrob and lead singer on "The Partridge Family," has died, according to his publicist Jo-Ann Geffen. He was 67.

The singer-actor had recently been admitted to the intensive care unit of a Fort Lauderdale, Florida, area hospital. Cassidy was in critical condition and suffering from organ failure before his death Tuesday, Geffen said.

"David died surrounded by those he loved, with joy in his heart and free from the pain that had gripped him for so long. Thank you for the abundance and support you have shown him these many years," she said.

Cassidy's nephew, Jack Cassidy, tweeted about his uncle's death, saying "I can't help but thank God for the joy that he brought to countless millions of people."

My uncle David Cassidy has sadly passed away tonight... & in the process of mourning I can't help but thank God for the joy that he brought to countless millions of people! I don't think I'm alone in saying that we will all miss him. God Speed!

David Cassidy was born into the entertainment industry that made him a star.

His father was famed actor and singer Jack Cassidy, and his mother was actress Evelyn Ward.

After his parents split in 1956, the elder Cassidy married actress and singer Shirley Jones the same year.

Cassidy moved in with his father, Jones and his three half-brothers after getting his high school diploma in 1968. His father helped him launch his career as an actor and musician.

"Long before he played my son on 'The Partridge Family,' David Cassidy was my stepson in real life. As a little boy, his sweet sensitivity and wicked sense of humor were already on display, and I will treasure the years we spent working and growing together," Shirley Jones said in a statement. Thank you for the enormous outpouring of affection you have offered our family at this difficult time."

When I was a little boy and my big brother would come to visit, the first call of business would be a punishing pillow fight. During the battle, he would regale me with hysterical stories of our father, often culminating in his taking a giant leap off my top bunk... — Shaun Cassidy (@shaunpcassidy) November 22, 2017

One of his half-brothers, Shaun Cassidy, tweeted about his memories.

"When I was a little boy and my big brother would come to visit, the first call of business would be a punishing pillow fight. During the battle, he would regale me with hysterical stories of our father, often culminating in his taking a giant leap off my top bunk. I tried to catch him of course. I always tried to catch him. But I never could. Now, I will carry him, along with all of the funny/sad/extraordinary days we shared, none more filled with love than these last few at his side," Shaun Cassidy wrote.

I️ have known, loved, and admired David Cassidy for 48 out of my 58 years. He has been as kind to me as any real brother could ever be. We've been through a lot together and he was always there for me. This loss is huge. RIP my dear friend. pic.twitter.com/eKdRyAuW2B — Danny Bonaduce (@TheDoochMan) November 22, 2017

Danny Bonaduce, who played Cassidy's little brother on "The Partidge Family," described his death as a "huge loss."

David Cassidy's early work included appearances on "Ironside," "Marcus Welby, M.D.," "Adam-12" and "Bonanza."

Photos: Heartthrob David Cassidy David Cassidy will be remembered as the popular '70s heartthrob who starred as singer Keith Patridge on TV's "The Partridge Family." Take a look at moments from his career and life. Hide Caption 1 of 19 Photos: Heartthrob David Cassidy "The Partridge Family," a sitcom about a mother and five children who formed a rock 'n' roll band, gave Cassidy a national audience for his music. Cassidy, who played Keith Partridge on the show, captured the spirit of 1970s youth. Hide Caption 2 of 19 Photos: Heartthrob David Cassidy David Cassidy with actress Barbara Sigel. His breathy voice and wholesome persona broke out from the small screen. At the time, his fan club reportedly was bigger than those of Elvis Presley and The Beatles. Hide Caption 3 of 19 Photos: Heartthrob David Cassidy Pictured here with his TV family, Cassidy would eventually tour the world singing hit songs such as "I Think I Love You" and filling concert halls with screaming teenage girls. Hide Caption 4 of 19 Photos: Heartthrob David Cassidy Cassidy wore a bunny suit in an episode of "The Partridge Family," titled "The Last of Howard." Hide Caption 5 of 19 Photos: Heartthrob David Cassidy Posters of Cassidy graced the walls of young girls everywhere in the early '70s. Here he poses on a horse. Hide Caption 6 of 19 Photos: Heartthrob David Cassidy Ever the ladies' man, Cassidy poses in a UCLA football uniform flanked by five cheerleaders. Hide Caption 7 of 19 Photos: Heartthrob David Cassidy David Cassidy and Kay Lenz at their wedding at The Little Church Of The West in Las Vegas in 1977. Hide Caption 8 of 19 Photos: Heartthrob David Cassidy Cassidy in concert in London in an undated photo. Hide Caption 9 of 19 Photos: Heartthrob David Cassidy Cassidy embraces new bride Meryl Tanz in Easton, Maryland, on December 15, 1984. Their marriage lasted only about a year. Hide Caption 10 of 19 Photos: Heartthrob David Cassidy Former Partridge Family cast members David Cassidy, left, Danny Bonaduce and Shirley Jones reunite on the "The Arsenio Hall Show" in July 1993. It was the first time the three had appeared together since the popular 1970s series left the air. Cassidy performed "I Think I Love You" during the taping. Hide Caption 11 of 19 Photos: Heartthrob David Cassidy Cassidy sings during the 1,000th performance of "EFX" in 1997 at the MGM Grand in Las Vegas. In just over two years, "EFX" drew more than 1 million showgoers with its blend of music, theater, dance, acrobatics and special effects. Creating the show cost a record $45 million. Hide Caption 12 of 19 Photos: Heartthrob David Cassidy Cassidy received the Hippest Fashion Plate - Male award for the role of Keith Partridge at the first annual TV Land Awards, which were taped at the Palladium in Hollywood on March 2, 2003.

Hide Caption 13 of 19 Photos: Heartthrob David Cassidy Cassidy sings the National Anthem before the start of a 2009 baseball game between the Boston Red Sox and Chicago White Sox at Fenway Park in Boston. Hide Caption 14 of 19 Photos: Heartthrob David Cassidy Cassidy in a "Once In a Lifetime" concert at the former LG Arena in Birmingham, England, on November 9, 2012. Hide Caption 15 of 19 Photos: Heartthrob David Cassidy Cassidy in a police booking photo after his arrest on charges of driving while intoxicated on August 21, 2013, in Schodack, New York. Hide Caption 16 of 19 Photos: Heartthrob David Cassidy Cassidy faces the media as he leaves town court in Schodack, New York, on September 3, 2014. The star was arrested for driving under the influence on three separate occasions between 2010 and 2014 and has spoken publicly about his struggles with alcohol.

Hide Caption 17 of 19 Photos: Heartthrob David Cassidy NBC News' Natalie Morales, Savannah Guthrie, Cassidy and Julien's Auctions' Martin Nolan appear on NBC News' "Today" show on March 21, 2013. Hide Caption 18 of 19 Photos: Heartthrob David Cassidy In this July 22, 2015, photo, Cassidy and girlfriend Maura Rossi pose in his five-bedroom home in Fort Lauderdale, Florida. Hide Caption 19 of 19

In 1970, Cassidy began playing the role of Keith Partridge on the musical sitcom "The Partridge Family." His stepmother, Jones, portrayed his mother, a widow with five children.

The popular ABC series ran for four years and also had a successful run in syndication.

The show also spurred several pop hits.

The single "I Think I Love You," featuring Cassidy on lead vocals, hit No. 1 on the Billboard charts in 1970 and sold more than 5 million copies. The songs "Doesn't Somebody Want To Be Wanted" and "I'll Meet You Halfway" also cracked the top 10 the next year.

The group was nominated for a best new artist Grammy.

Cassidy later launched a solo career, recording a dozen studio albums and six compilation albums.

After 'The Partridge Family'

He continued to work in television after "The Partridge Family" ended, performing in theater productions and briefly landing his own show, "David Cassidy - Man Undercover," which lasted a season.

Cassidy fared better in Las Vegas. He starred as the leading man of MGM Grand's "EFX" in 1996 and developed a show titled "At the Copa," which he co-starred in with Sheena Easton in 2000.

Cassidy released his autobiography, "Could It Be Forever? My Story," in 2007, writing about the pitfalls of fame and his failed first two marriages.

He had a daughter, Katie Cassidy, in 1986, from a relationship with Sherry Williams Benedon, and a son, Beau, with third wife Sue Shifrin, in 1991.

Cassidy hit some low points and ended up in rehab in 2014 after his third arrest for driving under the influence.

That same year Shifrin filed for divorce.

In 2017, Cassidy revealed that he was in the early stages of dementia, the same disease his mother and grandfather suffered from.

"To watch someone who raised you lose their mind and disappear is arguably the most painful thing I have ever experienced," Cassidy told CNN in a 2012 interview.

As for a career highlight Cassidy remembered fondly, he described the roar of a crowd that included his family at a 1972 performance at Madison Square Garden.

"It was so emotional for me. I was so blessed to have that moment with them," he told CNN in 2014. "It's the highlight of my life."

Celebrity reaction

Those who worked with Cassidy in the entertainment business shared their memories and condolences on social media.

I'm very sad to hear about David Cassidy. There were times in the mid-1970s when he would come over to my house and we even started writing a song together. He was a very talented and nice person. Love & Mercy to David and his family. — Brian Wilson (@BrianWilsonLive) November 22, 2017

Musician Brian Wilson of the Beach Boys said he and Cassidy once started writing a song together. "He was a very talented and nice person. Love & Mercy to David and his family."

#DavidCassidy. You were so sweet to me and you left us too soon. To me and millions of us you were forever young. RIP. pic.twitter.com/3JcjvKiUIA — Marlee Matlin (@MarleeMatlin) November 22, 2017

Actress Marlee Matlin tweeted, "To me and millions of us you were forever young."

Sad to learn David Cassidy has died. Like his father Jack he had great talent, and a complicated life. Condolences to his wonderful family. — Larry King (@kingsthings) November 22, 2017

Interviewer Larry King said, "Like his father Jack he had great talent, and a complicated life. Condolences to his wonderful family."

My heart is hurting. You were an amazing tv daddy! Proud and honored to have worked with one of the best. Love and Prayers #DavidCassidy — Alexa PenaVega (@alexavega) November 22, 2017

Alexa PenaVega worked with Cassidy on "Ruby & the Rockits," a 2009 TV show created by Shaun Cassidy, David's half-brother. She said Cassidy was "an amazing TV daddy."

so sad to hear of the passing of david cassidy... he was always so kind to me - such a pleasure to have had him on my show... sending love and prayers to his family... R.I.P. friend ❤️ pic.twitter.com/tsFkNiJzFc — Harry Connick Jr (@HarryConnickJR) November 22, 2017

Entertainers Harry Connick Jr. and Marie Osmond also shared memories.