Jack Nicholson found out his sister was actually his mother long after she had passed away

Jack Nicholson was nearly 40 when he learned the shocking truth about his family, one that could rival the plot of any of his most iconic films.

The Oscar winner grew up believing that his grandmother, Ethel May, was his mother and that his actual mother, June, was his sister.

That secret stayed buried for decades, only surfacing in 1974 during an interview for Time magazine as Chinatown was preparing to hit cinemas.

Born in 1937 in Neptune, New Jersey, Nicholson was the result of June’s teenage relationship with a married man.

To avoid scandal, the family decided that Ethel May would raise Jack as her son, while June would take on the role of his older sister.

According to biographer Patrick McGilligan in Jack’s Life, “nobody ever bothered to explain this to young Jack.”

June later left for Miami to chase her dreams as a showgirl, leaving Jack behind. At 17, he moved to Los Angeles to live with his “sister”, June, and start a new chapter.

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

Nicholson’s entry into Hollywood began humbly, working as an office boy in MGM’s cartoon department before taking up acting classes.

His big break came just as Chinatown was set for release, when researchers at Time uncovered the real story of his parentage.

Along with learning that June was his biological mother, it was also suggested that his father was still alive and living in Ocean Grove, New Jersey.

Nicholson, stunned, rang his brother-in-law Shorty, who initially denied the story before confirming it was true.

By then, both June and Ethel May had died, leaving Nicholson without the chance to confront them.

Still, he took the revelation in stride. He told Rolling Stone. “It’s dramatic, but it wasn’t traumatising. I was very impressed by their ability to keep the secret, if nothing else.”

“It’s done great things for me.”

The real-life twist eerily paralleled Chinatown, where Nicholson’s character unravels a disturbing family secret.

Though he’s occasionally joked about the situation, referring to June as his “sister-mother,” he has rarely spoken publicly about it since.