When Catherine Zeta-Jones Told Michael Douglas She Wanted to Be Monogamous, He Had to Break It Off with 5 Other Women

Michael Douglas says Catherine Zeta-Jones gave him an ultimatum early in their relationship

He was newly separated from Diandra Douglas and dating five women in different cities

Douglas and Zeta-Jones married in 1999 and share two children together

Michael Douglas had a few calls to make when Catherine Zeta-Jones made it clear she wasn't interested in sharing him.

In his new memoir, One Helluva Ride , Douglas, 82, looks back on the early days of his relationship with Zeta-Jones, 57, and reveals that the actress wasn't interested in becoming another relationship in his rotation. If he wanted to be with her, she made it clear, he had to be with her exclusively.

"She told me she understood that I was a single guy who'd come out of a long marriage, but she would only be monogamous," Douglas writes. "'I'm not interested in dating you if you're dating other people. You can either continue with them or end it and be with me.'"

Douglas had a pretty simple response, though he needed a minute — or, more specifically, five phone calls.

"I told her wait here I have to make five quick calls. 'Five? You have to make five calls?'" he recalls.

At the time, Douglas was still newly separated from his first wife, Diandra Douglas , whom he split from in 1995. He had been seeing five other women, though he says he viewed the arrangement as relatively straightforward.

"Just after my marriage, I had been seeing five other women. They knew I was recently separated and in the process of getting a divorce," he writes. "I made sure they all lived in different cities, which felt like a respectful way to be non-monogamous."

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According to Douglas, none of the women had asked him for something more serious or even questioned whether he was seeing anyone else.

"None of them asked for a commitment or even asked what else I was up to. I am sure they were seeing other people, too," he writes.

But once Zeta-Jones made her position clear, Douglas knew what he wanted to do.

"That day, I called each one to say I met somebody and would no longer be able to continue seeing them. They all took it well," he writes.

And just like that, five relationships were over and Douglas was all in on Zeta-Jones.

One Helluva Ride doesn't shy away from the romantic chapters that came before Douglas' life with Zeta-Jones. He writes candidly about his past affairs, including romantic entanglements with his Romancing the Stone costar Kathleen Turner and Basic Instinct costar Jeanne Tripplehorn .

By the time he met Zeta-Jones, however, Douglas was already completely smitten. He first saw her in an early screening of her 1998 film The Mask of Zorro , then happened to cross paths with her a few weeks later at the Deauville American Film Festival in France while he was promoting A Perfect Murder .

He asked his publicist to arrange a meeting over drinks, and he quickly found himself impressed by more than her beauty.

"She was smart, funny, unpretentious, and, yes, breathtakingly beautiful. She just seemed so confident and self-assured, too," Douglas recalls in the book.

Later, after a dinner with Zeta-Jones and her Zorro costar Antonio Banderas and his then-wife Melanie Griffith , Douglas was even more taken with her. There was just one problem: He admits he was "smashed" by the end of the night.

As he walked Zeta-Jones to the hotel elevator to say good night, Douglas blurted out what would become one of his most memorable lines: "I'm going to be the father of your children."

"It wasn't a cheap pickup line. It was the truth," he writes.

The pair went on to marry in 1999 and have two children, Dylan, 26, and Carys, 23 . Douglas also shares son Cameron , 47, with Diandra, 70.

Nearly 26 years later, Douglas' relationship with Zeta-Jones has only grown deeper.

"There's just an unknown at a certain point over time," he tells PEOPLE. "It goes beyond being attracted to somebody in this matter. It's just an unknown bond of being close and… a mutual respect."

One Helluva Ride by Michael Douglas is available now, wherever books are sold.

To watch the full interview, visit the PEOPLE App . For more from Michael Douglas, pick up the new issue of PEOPLE on newsstands everywhere Friday.