Kelsey Grammer Reveals His Marriage Mantra with Wife Kayte — and Whitney Houston Is Involved (Exclusive)

Kelsey Grammer is sharing the key to his 14-year marriage with his wife, Kayte Walsh — and it has a surprising connection to Whitney Houston.

“I always say, ‘Love is a contact sport,'” the Frasier alum tells PEOPLE. “Love Is a Contact Sport” is also the title of a 1987 Huston song.

“Once in a while you got to back it up with some action,” Grammer, 70, continues. “I just always try to say to myself, ‘Remember the blushing that you had when you first met. Remember that energy, that circulation that dialed you up just a little bit.'”

Grammer and Walsh, 46, a former flight attendant, got married in 2011. They share daughter Faith, 12, and sons Gabriel, 10, and James, 8. (Grammer is also dad to daughters Spencer, 41, Greer, 33, and Mason, 23, and son Jude, 20, from his past relationships.)

Grammer says Walsh was “very supportive” as he went through the process of writing about the brutal 1975 rape and murder of his 18-year-old sister Karen in his new book, Karen: A Brother Remembers, out May 6.

“When I finished the book, I turned her around and I said, ‘I’m finished.’ She said, ‘Well, I’ve missed you,'” Grammer recalls, tears welling up in his eyes. “I had to go away for a while — there were hours on end that I would just be staring off. But she was patient and loving through it. I had definitely lost a lot of the joy, and this brought it back for me.”

The book also provided a way for Grammer to make his sister known for more than just the worst thing that happened to her. He paints a picture of Karen as a free-spirited and loving woman who made the most of every moment, whose life was so much more than the way it ended.

“I wanted to breathe life into her and welcome her into the world,” he says. “We were Kelsey and Karen, brother and sister.”

In the time before her death, Karen had moved to Colorado Springs, Colo., after a semester at college in Georgia to be with her boyfriend. Grammer last spoke to his sister on June 30, 1975, and she told him she planned to come home to Florida after the Fourth of July.

When he didn’t hear from her again, Grammer called the local police. He later found out that just hours after he and Karen had chatted, she went to the Red Lobster where she worked at around 11 p.m. to wait for a friend to finish their shift.

A man named Freddie Glenn and two others had planned to rob the Red Lobster, but when they pulled up behind the restaurant, they spotted Karen. With a gun drawn, they told her to come with them. Karen was taken to Glenn’s car and was left with him as the other men entered the restaurant and ultimately decided against the robbery. When they returned, they found Karen tied up next to Glenn.

They drove her to one of the men’s apartments, where they took turns raping her. The men drove Karen to an alley, where Glenn stabbed her 42 times and nearly decapitated her. Glenn was convicted of Karen’s murder and several others in the area, and he’s currently serving a life sentence in prison.

While Grammer has said in the past that he forgives Glenn for his actions, he still holds him accountable.

“You don’t want to eat yourself to pieces because you can’t forgive somebody,” he says. “But it’s hard to forgive a person who consciously decided they wanted to murder somebody you love. This wasn’t just some temperance issue with him. It was deliberate. I can give you forgiveness, but you’re not going to get out of paying for it.”

It’s a lesson he’s teaching his younger kids, along with encouraging them not to hold onto anger.

“They say stuff all the time, like, ‘I want to kill [Freddie Glenn],’” he says. “I tell them, ‘I understand it and respect you for it, but you’re going to want more from life than that.’”

Karen: A Brother Remembers fittingly ends with Grammer’s pilgrimage to Colorado Springs to retrace Karen’s last steps.

“I had to complete my farewell to her. I had to be there and hold her in the end,” he says. “It became important to get the closure. I hate clichéd words like closure, but I got the opportunity to say all the things I never said.”