"He was totally involved with his kids," photographer Arthur Grace tells PEOPLE of Robin Williams
Credit: All Photographs © Arthur Grace/Contact Press Images from "Robin Williams: A Singular Portrait 1986-2002" (Counterpoint Press, 2016)

Robin Williams shocked the world when he ended his life in August 2014, leaving behind a legacy of laughter and kindheartedness. But the star was so much more than Hollywood’s beloved humorist – he was also a devoted father.

In Arthur Grace‘s new book, Robin Williams: A Singular Portrait, 1986-2002, Williams’ life out of the spotlight and at home with children Cody, now 24, Zelda, 26, and Zak, 33, is on touching display.

The photographer shares images from his longtime friendship with the star, whom he first met while photographing him for Newsweek in 1986.

Over the years, Grace photographed his famous friend often, and he looked forward to the day “when I was 84 and Robin was 80 and we would reminisce and put together a book.”

With Williams gone, Grace, 69, handled the task on his own – a little ahead of schedule.

“He was totally involved with his kids,” Grace tells PEOPLE of Williams, adding of the intimate photographs, “One of his biggest regrets was having to spend time away when he was working.”

Grace explains that Williams, who was 63 when he died, “loved to play games with his kids, read them stories.”

“He loved to snowboard with Zak and did puzzles with Zelda. When he was with his kids was when he really lit up.”

Zak was Williams’ son with first wife Valerie Velardi, and Zelda and Cody’s mother was Marsha Graces, the actor’s spouse from 1989-2010.

For more of Arthur Grace’s intimate photographs of Robin Williams, pick up the latest issue of PEOPLE, on newsstands Friday

Grace also tells PEOPLE about Williams’ kindhearted nature, explaining of his own 1988 wedding, “Robin hosted a dinner for me and my wife and then put us up at the Carlyle Hotel with a bottle of champagne.”

He concludes, “He was the funniest man on the planet.”