Hugh Hefner: His Revolutionary Life in Pictures

"I was always a dreamer," Hefner told PEOPLE in an exclusive interview in 2016 before his 90th birthday. "And I did everything I could to make that dream come true."

"I had a happy childhood," Hefner said (left, with mother Grace, younger brother Keith and father Glenn in 1934). At just 27, he fulfilled a lifelong dream of launching his own men's magazine. Playboy's inaugural issue featured never-before-seen nude photos of Marilyn Monroe; the magazine was an instant success. Three marriages, four children and many younger girlfriends would follow, but Hefner never strayed from a commitment to the iconic brand he started. The magazine stopped running nude photos last month; still, Hefner insisted, "Playboy is a fantasy life for a lot of people. Including me."

As he worked tirelessly to launch Playboy, Hefner (here in 1953) confessed he was "an absent dad" to children Christie, now 63, and David, now 60 (with first wife Millie).

His hard work paid off. Hefner was aware there was a market for a men's magazine, and scraped together $8,000 from family and friends to publish the first issue of Playboy with Marilyn Monroe on the cover in December 1953. It was a hit and sold over 50,000 copies.

"The magazine was about breaking barriers," Hefner said, pictured with his Playboy Club bunnies circa 1960. "It wasn't just a sexual thing."

The success of Playboy led Hefner to seek out other forms of media, mainly television. He began hosting his own show, Playboy's Penthouse, in the late 1950s and early '60s. The show featured the founder in a tuxedo and smoking a pipe surrounded by "playmates" and interviewing celebrities like Sammy Davis Jr. and Don Adams.

Hefner bought the Holmby Hills, California, Playboy Mansion in 1971 for $1.1 million; and it sold to a neighbor in August 2016. While the initial asking price was listed at $200 million, the actual sales tag was not disclosed. Hefner's only stipulation: The buyer had to allow him to remain in the home until his death.

Hefner married model Kimberley Conrad at age 63 (she was 26). "I was ready to be a dad again," Hefner said of their sons Cooper and Marston (pictured in 1993).

"They both love women," the media mogul said of former Mansion fixtures Warren Beatty and Jack Nicholson (pictured in 1986).

Hefner continued to expand his empire into the 21st century with the hit E! reality TV series The Girls Next Door, starring real-life girlfriends (from left) Bridget Marquardt, Holly Madison and Kendra Wilkinson. His popularity was sustained through cameos in TV shows and films, such as The House Bunny, which was inspired by Playboy.

"Crystal is one in a million," Hefner said of his then-31-year-old wife (pictured on their 2012 wedding day). "I don't think about the age difference. We're very happy."

Cooper Hefner was named Chief Creative Officer of the magazine in 2016, and addressed his father's health in August 2017. "It's tough to watch him struggle," Cooper said in an interview with The Hollywood Reporter. "But I'm just happy it's physical and not mental."

Hefner died from natural causes at the Playboy Mansion "surrounded by loved ones" on Sept. 27, 2017, a rep for the Playboy Enterprises founder said in a statement to PEOPLE. He was 91.