“My daughter fought for a long time with extreme mental health,” the 76-year-old added. “Borderline personality disorder, other things, and did the best she could until she couldn’t.”

But as much as he understood the challenges Katherine lived with, it hasn’t made the heartbreak any easier to navigate for him and his sons Oliver, 40, and Henry, 36.

“I was getting in the car that day,” he recalled of the day his daughter died. “And I was thinking, ‘Okay, I’m 75. Why am I continuing? Like, really? What is the point of this?’”

But when the Only Murders in the Building star arrived at Oliver’s home in Newport Beach, California, where he lives with his wife Haylen Short, Martin remembered.  

“I got to Newport, and these two grandsons, five and four just jumped, ‘Papa, Let’s play giant,’” he recalled. “And suddenly you go, ‘Oh, that’s why. That’s why.’”

For a look back at Martin’s happiest family memories, keep reading…