When Bill Gates married Melinda, there was a condition. He could go on a yearly holiday with his ex.

Money can buy you many things — but not the love of the woman who met you before you became a billionaire.

In a new interview, Bill Gates told the Times of London that he regrets his 2021 divorce from Melinda French Gates.

"That was the mistake I most regret," he said.

"There is a certain wonderfulness to spending your entire adult life with one person because of the memories and depth of things you have done and having kids together.

"When Melinda and I met, I was fairly successful but not ridiculously successful — that came during the time that we were together. So, she saw me through a lot. When we got divorced it was tough."

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Bill and Melinda met at a work dinner after she began working at Microsoft as a product manager in 1987.

"I was definitely attracted to his brilliant mind, but beyond that, his curiosity," Melinda told Fortune in 2015. "And he has a huge sense of fun. I love that wry side of him."

Their relationship was just casual at first, before they found themselves at a crossroads.

"She had other boyfriends, and I had Microsoft," Bill said in 2019 Netflix series Inside Bill's Brain.

"We were like, 'Hey we are not really serious about each other, are we? We are not going to demand each other's time.'"

Melinda felt the same: "I was new to Microsoft, there were a lot of men there and ... you are still looking around."

Melinda and Bill Gates in 1998. Image: Getty.

But after about a year, "sort of to our surprise, certainly my surprise, we said, 'Hey, I love you'," Bill said.

"And she said she loved me and then it was like, 'Wow, and now what is going to happen?... You know, we cared a lot for each other and there were only two possibilities: either, we were going to break up or we were going to get married."

Bill took the commitment of marriage seriously, and was worried that he would not have enough time to dedicate to a marriage while still running Microsoft.

One day, Melinda walked into his bedroom to find him making a list: "His whiteboard had the pros and the cons of getting married," she recalled, laughing.

The pros must have been longer than the cons, because on New Year's Day 1994 they married in Lanai, Hawaii.

The wedding was kept extremely secret, costing more than US$1million. Gates had bought out all the available rooms at the island's 250-room hotel to keep media from staying there and reportedly hired out all the helicopters on Maui to keep photographers from flying over the wedding.

Two years later, the couple welcomed their first child, daughter Jennifer, now 28 and a doctor.

They have two other children: son Rory, 25, and daughter Phoebe, 22.

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A post shared by Melinda French Gates (@melindafrenchgates)

For both Bill and Melinda, equality in their relationship was important.

"We certainly weren't working as equals when we started together. I was down several levels at Microsoft, and he was the CEO," Melinda recalled to Fortune.

"We've had to change to really be coequals. It's not something that immediately happens overnight, but we're both committed to it. We needed to talk behind the scenes when it wasn't working. But I think that's come now."

In 2019, she told CNBC that they had to work to ensure they weren't falling "back into our own sort of biases about who does what".

She gave an example of the conversations that took place when eldest daughter Jennifer was starting school.

They'd enrolled her in a school that meant a 45 minutes round-trip, but Melinda realised that would mean she'd waste a lot of time waiting in traffic, so she suggested a school closer to home, but Bill was convinced they'd found the perfect school.

"So Bill said, 'What could I do? What could I do to make it easier?' And I said, 'Well, you could drive,'" she explained. So he did, and they shared school drop-off duties.

"Three weeks in, I started to notice more dads were driving and showing up with their kids," Melinda recalled. "And a mum said to me, 'Do you see what’s going on here?' And I was like, 'Well, I don't know. More dads are dropping off.

"And she says, 'Yeah, we went home with our hands on hips and said, 'If Bill Gates can drive his kids to school, then by gosh, you can too!'"

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Following their divorce announcement, it came to light that Bill was holidaying every year with his ex-girlfriend, Ann Winblad, a tradition that started when they began dating in 1984 after meeting at a computer conference.

The tradition to spend a long weekend together at a cottage in North Carolina continued after the pair broke up in 1987 and according to a 1997 Time profile, the holidays with Ann was part of the deal when he married Melinda.

“We can play putt-putt while discussing biotechnology,” Bill said of his weekend getaways with Ann, who is a software expert and venture capitalist from Seattle.

Ann added to Time, “We share our thoughts about the world and ourselves.

“And we marvel about how, as two young overachievers, we began a great adventure on the fringes of a little-known industry and it landed us at the centre of an amazing universe."

Ann Winblad, an entrepreneur and businesswoman, in 1984. Image: Getty.

The pair were so close that Bill sought Ann's advice before proposing to Melinda.

"When I was off on my own thinking about marrying Melinda, I called Ann and asked for her approval," he said.

Ann approved, recalling, "I said she'd be a good match for him because she had intellectual stamina."

Bill and Melinda are among the world's most prolific philanthropists. The Bill & Melinda Gates Foundation was launched in 2000, a merging of two previous Gates' foundations, the William H. Gates Foundation and the Gates Learning Foundation.

Bill was Microsoft's CEO until 2000 and since then has gradually scaled back his involvement in the company he started with Paul Allen in 1975.

He transitioned out of a day-to-day role in Microsoft in 2008 and served as chairman of the board until 2014.

Melinda and Bill Gates meeting the Queen in 2005. Image: Getty.

Melinda said in their 2018 annual letter that when Bill first came to the foundation, he was used to being in charge.

"I'd stayed home with our kids, so I was restarting my career," she wrote.

"There were times I felt that disparity - in meetings when I was reticent and he was voluble, or when the person we were meeting with looked toward Bill and not me. It's always been important to us that we are equal partners in our foundation's work. We've learned over time to give each other feedback at home about times in the office when we didn't meet that goal. And we're better for it."

Bill agreed: "Our occasional disagreements these days are over tactics. Because I've been a public figure longer, and because I'm a man, some people assume I am making the big decisions. That's never been the case.

"Some people see Melinda as the heart of our foundation, the emotional core. But just as she knows I'm more emotional than people realise, I know she's more analytical than people realise. When I get really enthusiastic about something, I count on her to make sure I'm being realistic... We are partners in both senses that people use the word these days: at home and at work."

Melinda and Bill Gates in 2018. Image: Getty.

The couple said in the statement announcing their divorce they would continue to co-run the foundation, which works on global health and development issues like eradicating polio, improving sanitation systems in impoverished countries and developing clean, affordable energy.

In 2020, Bill, formerly the world's richest person thanks to co-founding Microsoft in 1975, said he was stepping down from the company's board to focus on philanthropy.

In the years following their divorce, the former couple continued to run the foundation together. However, Melinda left last year.

"The time is right for me to move forward into the next chapter of my philanthropy," she shared in a statement.

When it comes to their relationships, these days, Bill, 69, has found comfort with Paula Hurd, widow of former Oracle CEO Mark Hurd. Meanwhile, Melinda, 60, is rumoured to be dating philanthropist Philip Vaughn.

— with AAP.

This article was originally published in May 2021, and has since been updated with new information.

Feature image: Getty.