Kaitlin Olson mourns dad's death after valiant battle: 'My forever favourite'

Kaitlin Olson is sharing fond memories of her dad.

On Monday, May 18, the High Potential actress revealed her father, Don Olson, passed away, sharing a poignant Instagram post, describing him as "my first love, my initial protector, and my perpetual favourite person."

"Honestly, sharing this on social networks doesn't feel quite right. It’s incredibly personal and sensitive. But pretending life continues as usual, as if the most devastating event didn’t just occur, seems even more wrong," Olson, 50, wrote alongside a series of photographs. "As if everything meaningful hadn't just abruptly ceased."

Olson further shared her thoughts, mentioning how her father "struggled tirelessly for a long time to remain with us."

"Words fail me right now. None are adequate to describe his essence," she conveyed. "Being blessed with him as my father was the best thing in my life. Perhaps the second blessing was to be with him during his final moments. I cherish you, dad. I will honour all my promises, just like you did."

In her message, the It's Always Sunny in Philadelphia actress included a recent picture with her father, several past images from her childhood with him, a photo of him with her husband Rob Mac, and a picture of her holding his hand. "Words fail me," noted Mac, 49, in the comments. "He was truly unique."

He further commented, "My lifelong ambition is to embody even half of the man he was. I've never witnessed anyone love someone as he loved you. I feel fortunate he was part of my life and proud to have been his son for these past 17 years."

According to the Portland Tribune, Don was the newspaper's publisher between 2000 and 2001. In a 2017 interview with the Tribune, he mentioned his lack of surprise concerning his daughter's professional path, stating "she certainly exudes passion."

“While she was at university, I occasionally suggested a secondary career path. Something as a backup plan,” he recalled. “However, she remained steadfastly dedicated to her passion.”

Kaitlin and Mac are parents to two sons: Leo, 14, and Axel, 15. Both shared with PEOPLE during the grand opening of Broadway's The Lost Boys on April 26 their approach to thriving as parents and maintaining “purposefulness” in scheduling their time. "Our children are our priority," she explained. "It's all about ample communication, managing our commitments, and ensuring family comes first."

"We adore our work, but we love each other even more, and we understand the importance of being happy at home. If our children, pets, and family needs aren't tended to, it just won't work," Mac added.