On Friday, the Arrow actress shared a heartbreaking tweet honoring the late star, who died of organ failure Tuesday at the age of 67.
“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.”
The Partridge Family star and Katie, 30, had a complicated relationship: Though Katie was raised by her mother, former model Sherry Williams, and her stepfather, Richard Benedon, David still played a role in her life.
“Because I didn’t raise her, I didn’t have to parent her,” David told PEOPLE in 2009. “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 said at the time. “It’s nice when your dad can be your friend.”
But over time, the pair drifted apart. In February, David confessed to PEOPLE that the two were no longer in contact.
“I wasn’t her father. I was her biological father but I didn’t raise her. She has a completely different life,” he explained. “[But] I’m proud of her. She’s very talented. It’s hard for me to even accept how old she is now.”
David 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.”
In addition to Katie, David is survived by son Beau Cassidy; brothers Shaun, Patrick and Ryan; stepmother Shirley Jones; and numerous nieces, nephews and cousins. Plans for a memorial and funeral service have not yet been disclosed.