Shaun Cassidy Calls Late Dad Jack Cassidy a 'Phony,' Claims He Invented an Accent

Shaun Cassidy is offering an unfiltered look back at his father Jack Cassidy, describing the late actor as brilliant yet deeply complicated.

Shaun Cassidy is reflecting on his father Jack Cassidy's complex persona, calling him a "phony" in public life.

"My dad was so complicated," the former teen idol, 66, exclusively told PEOPLE. "He basically invented this public persona with an accent that didn't exist in any country ever."

Jack, who was born in New York City, grew up in a family of engineers and was expected to pursue a similar path. Instead, after experiencing the magic of Broadway at age 14, he turned to the stage and began building a career in entertainment.

As his fame grew, particularly through his role on "He & She," Jack often appeared on talk shows. There, he adopted a quasi-British accent that puzzled his children. At home, Shaun and his brothers Patrick, 63, and Ryan, 59, never heard the same manner of speech.

"Patrick and Ryan and I would be like, 'What is up with this dude?' " Shaun recalled. "I mean, it seemed so phony to us, and that wasn't like who he was. I'm not sure he ever really figured out who he was."

Jack Cassidy's life was cut short in 1976 when he died in an apartment fire at the age of 49.

"He was not a good father — and I don't say that with disrespect. I just say it with objectivity," Shaun said. "And yet I wouldn't have traded him for the world. I got so many gifts from him, so many."

Despite those gifts, Shaun noted that his father was not particularly present while he was growing up.

Jack married actress Shirley Jones in 1956, and the couple divorced in 1975. According to Shaun, their public image as a glamorous Hollywood pair did not reflect who they truly were.