At 37, Jack Nicholson had no idea his "sister" was his mother. So a reporter told him.

Like all productive afternoons, this week I found myself in the depths of Reddit trawling through break-up predicaments and confessional long-reads before I stumbled on something that caught my eye.

Jack Nicholson didn’t know who his mother was until a reporter told him, it read.

That sounds…wrong? I thought. Or unethical on behalf of the reporter? Or maybe just great clickbait?

I dug a bit deeper. I’ve always been interested in the fully-formed lives that sit far behind the facade and bright lights of Hollywood. The untold stories that shape the well-known faces brandished on the big screen.

What I found, though, was that it wasn’t wrong, or even clickbait. It was totally on the money.

All the way back in 1974, Jack Nicholson’s movie Chinatown was opening in theatres, Nicholson was on the press tour and Time Magazine had chosen to do a cover story on him.

In the research stage, a Time reporter decided to phone the then 37-year-old actor and do some fact-checking after the magazine had stumbled on an extraordinary tip: Jack’s “sister” June was in fact Jack’s mother, and a man claiming to be his father was alive and well in Ocean Grove, New Jersey.

When the question was posed to Nicholson, both his “sister” June and “mother” Ethel were dead. So he denied the information on the basis of ignorance. However, it wasn’t until his other “sister” Lorraine confirmed the rumour that Nicholson finally learned the truth.

Nicholson had in fact been born to illegitimately to 17-year-old June Nicholson. As June was so young and unmarried, her parents agreed to raise their grandson without letting slip who his real parents are.

"I'd say it was a pretty dramatic event, but it wasn't what I'd call traumatising," Nicholson said later about the discovery.

"After all, by the time I found out who my mother was, I was pretty well psychologically formed. As a matter of fact, it made quite a few things clearer to me. If anything, I felt grateful."

However, he never found out who his father was, as that was a secret both Ethel and June took to the grave.