How Jack Nicholson discovered his sister was actually his mum after they both passed away

Jack Nicholson has played some of the most complex and intense characters in Hollywood history, but one of the most shocking twists of his life happened off-screen.

The Shining actor spent nearly four decades believing the woman who raised him was his mother, until he learned the truth, which he called the 'most f***ed thing [he'd] ever heard'.

Born in 1937 in Neptune, New Jersey, Jack Nicholson’s early life was built on a carefully guarded family secret. His real mother, June, was only 18 when she became pregnant.

The father, a man named Don, was already married to someone else. To avoid scandal, June’s mother, Ethel May (Nicholson's grandmother), stepped in and took on the role of Jack’s mum, while June was introduced to him as his much older sister, and his aunt Lorraine, June's sister, as his other sibling.

As a young woman, June left New Jersey for Miami, hoping to make it as a showgirl, while Jack stayed behind with who he believed was his mother, Ethel May.

The actor was kept in the dark for many years (Allen Berezovsky/Getty Images)

At 17, Nicholson left for Los Angeles, where June had relocated to chase a career in entertainment.

“Since my only relative in the world was June, who was out here, I came out to look around,” he told Rolling Stone in 1986.

His Hollywood journey began in the animated cartoon department at MGM Studios, where he worked as an office boy. It didn’t take long before his charm and natural talent were noticed, leading him to pursue acting, an endeavour that would change his life forever.

Everything Jack knew about his family changed in 1974 however, just as his critically acclaimed film Chinatown was about to hit cinemas.

Researchers for Time magazine, preparing a profile on the rising star, uncovered the truth: Ethel May, the woman he thought was his mother, was actually his grandmother, and his ‘sister’ June was, in fact, his biological mother.

Even more shocking, they claimed that his father was still alive and living in Ocean Grove, New Jersey. Stunned by the news, Jack immediately called his biological aunt Lorraine's husband Shorty, demanding answers.

Nicholson and Faye Dunaway in Chinatown (Bettman/Getty Images)

“This is the most f***ed thing I’ve ever heard,” he reportedly said, according to Patrick McGilligan, author of Nicholson biography Jack’s Life. “A guy calls me on the phone, and says that my father is still alive, and that Ethel May wasn’t really my mother, that June was my mother.”

Initially, Shorty denied the claims, but eventually admitted they were true, although he couldn't confirm if the man the researchers had found was really his biological father.

By this time, both June and Ethel May had already died, meaning the actor was never able to confront them.

But despite the 'dramatic' revelation, he insisted it wasn’t something that deeply ‘traumatised’ him.

“I was very impressed by their ability to keep the secret, if nothing else,” he later said in an interview with Rolling Stone.

“It’s done great things for me.”

Although he has since jokingly referred to June as his ‘sister-mother’ in interviews, Nicholson rarely speaks publicly about the discovery.