The 70-year-old actor's younger sister Karen was abducted, raped and murdered in 1975 and although he was 300km away at the time, Kelsey had never forgiven himself for not being able to protect her.
However, he revealed that writing the book Karen: A Brother Remembers 50 years later, has finally helped him to come to terms with his grief and guilt.
He told Us Weekly: "It's been amazing. I don't carry the self-loathing part anymore. I don't blame myself anymore. I just miss her.
"The whole idea was to bring Karen here to remember her. People have said, 'Wow, I really feel like I got to know her,' and that's what I wanted to do. And also release myself from some of the guilt I've lived with for a long time.
"(The book) is definitely joyful. For a long time, the grief was in the ascendancy and stayed there. And finally, the joy kind of crept back. They live evenly now - maybe even a little weighted more toward the joy. If there's one thing I hope I can pass on to people who've suffered similar grief, it's to look back on the life [the person] lived rather than the life they lost."
However, Frasier star Grammer admitted that going back over the details of Karen's death was traumatic.
He said: "It was really hard. I would sometimes disappear down a sadness I couldn't shake. After I read the police report, I couldn't do a thing for about three weeks. I had to take a break.
"I was able to discover things about her that were equally remarkable in the moment. Things I kind of knew anyway, but the fact that she crawled as far as she did, and staggered as much as she did in those last moments of her life, was really heartbreaking.Â
"(It was) very difficult to go through, but it felt like I had to be there. I had to walk those steps with her."
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