“I was saddened to hear of the passing of my ‘brother’ David Cassidy,” Partridge Family star Forster tells PEOPLE exclusively. “It’s hard to imagine, really.”
The two starred on the beloved musical sitcom, which ran from 1970-74. Starring Cassidy’s real-life stepmother Shirley Jones as a widow, Cassidy played the eldest of her five children, Keith Partridge, as the family embarked on a music career together.
“David was very kind to me and really was like my older brother during The Partridge Family,” says Forster, 57. “One year, he even gave me a Swiss army knife for Christmas, which I still have. He also gave me a singing lesson when I expressed an interest in singing!”
“In spite of his crazy concert schedule on the weekends, he would arrive at the studio prepared and we would have a lot of fun during shooting and between takes,” he continues. “He’d fly back from wherever and arrive at 2 o’clock in the morning and come to the studio. He’d be tired, but he was always really nice and professional.”
“He was a very talented actor and I often admired the emotion he could put into his character,” he adds. “Needless to say, he was also a wonderful singer and his breathy style made many young girls swoon!”
Cassidy had “the full package,” according to Forster.
“I was just reading an editorial about how he fit in with the time and his squeaky clean image, and yet he was sexy on the side, and that was a big part of his charisma,” he says.
Despite Cassidy’s “insane popularity,” Forster says the star always made everyone on set “feel very comfortable and part of the team.”
“It was a really good experience … we would have plenty of laughs and good times,” recalls Forster. “He was always really gracious to me.”
Forster said the two didn’t see each other for “many years” after their lives went separate ways when the show wrapped, but he always enjoyed their reunions.
“In the last 20 years or so, we would be reunited while doing Partridge Family reunion shows,” said Forster. “[It was] always nice to see him again, and I particularly enjoyed time spent with him the night before we were on the Today show in New York around 2009. My thoughts go out to his friends, his fans, and most of all, his family during this difficult time.”
Cassidy publicly admitted his struggle with alcohol abuse in 2008. He also battled substance abuse issues, which involved a stint in rehab in 2014 .
“The poor guy, he was always having to sort of live up to an image that wasn’t really his,” says Forster. “From the beginning he wanted to be a rock star along the lines of Jimmy Hendrix and he lands Partridge Family and has to go a different route, so I know it sort of haunted him the rest of his time. He was touring and on stage, but he spent most of his time doing Partridge Family songs.”
“It’s like if you’re the Beach Boys and everyone wants to hear ‘Surfin’ Safari’ 3,000 times,” adds Foster. “You can play your new stuff, but remember the audience is there to hear what you’re famous for, which in his case is ‘I Think I Love You’ and things like that. But he stuck with it. He could have just withdrawn, but he kept at it and I give him props for that.”
Forster is grateful that through his work, Cassidy will be able to live on “for eternity in some way.”
“Fans will be able to put his albums on and take themselves back to a happier time,” he says. “I hope he took solace in that. I know he struggled with things for a long time, and I hope that in the end his son and daughter maybe provided him with a joy that he really wanted.”
Cassidy’s real-life brother Shaun also remembered the late star in a touching tribute on Tuesday.
“I tried to catch him of course. I always tried to catch him. But I never could,” tweeted Shaun alongside an old photo of the two as kids.
“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,” he said.
...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. pic.twitter.com/nc4w9HdTLC— Shaun Cassidy (@shaunpcassidy) November 22, 2017
Cassidy had been in intensive care since he was hospitalized for liver and kidney failure last week.
“On behalf of the entire Cassidy family, it is with great sadness that we announce the passing of our father, our uncle, and our dear brother, David Cassidy,” his family said in a statement to PEOPLE on Tuesday. “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.”