In 2009, PEOPLE caught up with the Partridge Family star and the 31-year-old actress to discuss their unique father-daughter relationship.
Though Katie was raised by her mother — former model Sherry Williams — and her stepfather, Richard Benedon, Cassidy still played an important role in her life.
“Because I didn’t raise her, I didn’t have to parent her,” he said. “I’m always here and totally nonjudgmental.”
“To be able to go to someone I’m genetically linked to, tell them anything and know that they’re not going to judge me — it’s unbelievable,” Katie added. “It’s nice when your dad can be your friend.”
But Cassidy, who suffered from dementia toward the end of his life, wasn’t just a friend — he was also a strong mentor with great advice.
“Do not work for money,” he told his daughter. “Do not work for fame. Work for the work. And if you get a great role and they offer you nothing, take it.”
And Katie took that advice. “That’s all he’s said, and I’ve taken the advice,” she told PEOPLE.
Despite their close relationship seven years years ago, Cassidy confessed that he was no longer in contact with his eldest child.
“I wasn’t her father. I was her biological father but I didn’t raise her,” he exclusively told PEOPLE. “She has a completely different life.”
Although the father-daughter duo had a falling out, he was still impressed with the woman she had become.
“I’m proud of her,” Cassidy added. “She’s very talented. It’s hard for me to even accept how old she is now, like 30.”
And Katie was among the family members who rushed to Cassidy’s side when he was hospitalized last month.
On Nov. 21, the ’70s teen heartthrob died of organ failure at the age of 67. A few days after his death, the Arrow actress shared a heartbreaking tweet honoring the late star.
“Words cant express the solace our family’s received from all the love & support during this trying time,” she wrote. “My father’s last words were ‘So much wasted time.’ This will be a daily reminder for me to share my gratitude with those I love as to never waste another minute… Thank you.”