There are friends whose weddings you go to, whose vows you echo and whose joy you toast – all while wondering how long it will last.
Then there are couples like Bill and Melinda Gates, who appear for all the world like nailed-on 'til death do us part-ers – too sensible, too devoted to give in to hot-headed disputes that can end a long-term marriage.
Perhaps that's why news of their split is so gloomy. If anyone was going to make a lifetime's go of it, surely it was them?
For run-of-the-mill celebrities, relationship drama is practically in the job description. For other tech billionaires, you can see it coming.
Jeff Bezos bulking up in the gym was a giant warning light, and thrice-divorced father of seven Elon Musk doesn't appear to be a model of marital harmony.
But steady-as-you-go, 27-years-together, life of dedication to good causes, chinos-wearing Bill and Melinda? Surely not them.
If their marriage is, as they claim in court documents, "irretrievably broken", then it feels like we're all doomed.
It was, after all, only two years ago, on the silver wedding anniversary, that Bill posted a video of him cutting their wedding cake and Melinda gushingly responded: "I thought my heart was full that night, but the last 25 years have taught me just how full a heart can get".
So what on earth could have gone wrong?
Although the news of the Gates' separation may have seemed a bolt from the blue, there are hints that something has clearly been rumbling.
"It's been a challenging stretch of time for our whole family," wrote their eldest daughter Jennifer, 25, though she confessed her feelings were still raw. "I'm still learning how to best support my own process and emotions as well as my family members at this time."
One of the most significant "family members" in this story, however, is missing. Bill's father, Bill Senior, a lawyer and himself a philanthropist, was a man whose values were pivotal not just in his son's life but in bringing and keeping his son and daughter-in-law together.
Indeed, in the Gates dynasty, the tech billionaire son always referred to his father as "the real Bill Gates – all the things the other one aspires to be". It was, then, inevitably devastating when in September last year Bill Gates snr died from Alzheimer's aged 94.
Not easily given to emotion, Bill jnr posted a tender and intimate portrait of his father online: "Dad lived a long and enormously meaningful life. I never stopped learning from his wisdom, kindness, and humility." Above all, he wrote, "Melinda and I owe him a special debt."
The Gates family that young Microsoft product manager Melinda French was attracted to after she started dating Bill in 1987 was a Gates family shot through with the personality of her future father-in-law. "He was the bridge between them, the glue," said one observer who knows Bill. "This wouldn't have happened before he died."
In so many ways this is a split beyond the comprehension of ordinary mortals. How could it be otherwise, when the principals are between them worth more than US$130 billion ($181b)?
But some of the stresses and strains in their marriage are, despite all that, deeply familiar, and rooted in the simple business of - for all their wealth and privilege – doing the dishes and bringing up the children.
In her book, The Moment of Lift: How Empowering Women Changes the World, Melinda writes of growing frustrated by always being the one to clean up after supper. A fiercely independent woman who gave up her career to raise their family, she found herself carrying the burden of domestic duties. Only in 2001, a year after he stepped down as Microsoft CEO, did her husband start doing the odd school run.
Raising Jennifer and her younger brother Rory, 21, and sister Phoebe, has been – as it is for many couples – a project that sometimes divides, but more often than not, unites.
"Over the last 27 years," the pair wrote, "we have raised three incredible children and built a foundation that works all over the world." It's clear they view their children and the Bill and Melinda Gates Foundation as the twin pillars, the two great achievements, of their married life.
But Phoebe is now 18. How many couples stay together, tough it out in the hard times, for the children? And there have been hard times. "I can remember some days that were so incredibly hard in our marriage where you thought, 'Can I do this?'" Melinda said in 2019.
The bottom line and the other 'woman'
Whatever their disagreements, Bill and Melinda Gates have always been united on one thing – the desire to give their money away. Cash is unlikely to be behind this split.
Indeed, on a trip to Africa while they were engaged, a few years after Bill, at 31, had become the world's youngest billionaire, they jointly decided that, as Melinda put it, "the vast majority of resources from Microsoft [which Gates co-founded] would go back to society".
There was never any dispute. It was, Melinda said, "an easy discussion" and, although their lifestyle is hardly spartan (they live in a US$125 million, 61,500 sq m mansion called Xanadu 2.0 overlooking Lake Washington, a few miles outside Seattle), they are determined to give away their wealth – the children will reportedly get US$10m each, a fraction of a fraction of a per cent of the family fortune.
Although their personal lives are going in separate directions, the pair have also made it clear that they will continue to run the foundation together.
Nor is there any suggestion that anyone else is involved. Bezos, of course, famously left his wife Mackenzie for the broadcaster Lauren Sanchez.
Melinda was even apparently happy to let Bill head off each year to spend a weekend with his ex-girlfriend, software entrepreneur Ann Winblad, at her beach house in North Carolina. Yet it was innocent, even geeky fun. "We play putt-putt while discussing biotechnology," Gates once said.
Winblad, who is five years older than Gates, was the "one before the one". They split in 1987, the year he met Melinda, and remained on good terms: he even called her and asked her to sanction his marriage.
Winblad did so because she thought Melinda had the brains not to bore, or be bored by Bill. "Intellectual stamina," she called it.
Indeed, if there was "another woman" in Bill Gates' life, it was always his career – first his fierce focus on establishing Microsoft and crushing the competition, and secondly his intense desire to address global ills through the foundation.
In the early days of dating, this little "something on the side" was understood. "She had other boyfriends," Gates said in the documentary Inside Bill's Brain, "and I had Microsoft."
Not always so cuddly
One doesn't necessarily become a tech titan by being easy going. It's hard to remember, now that he is the epitome of an avuncular academic philanthropist, that Bill Gates was once deeply feared, unforgiving and ruthlessly competitive, so desperate to establish his company as the peerless global leader that Microsoft was eventually taken to court by the US government on monopoly charges.
He was, and clearly remained, deeply uncompromising on aspects of his life that were of supreme importance to him.
His wife would tell the story of how, when in 2013 she wanted to co-write the forward to their foundation's annual report, he refused. "It got hot," Melinda wrote in The Moment of Lift. "Bill said the process had been working well and he didn't see why it should change."
Eventually, after several years of compromise, the couple did co-sign the letter. But as Melinda has said: "He's had to learn how to be an equal, and I've had to learn how to step up and be an equal."
Too much time in lockdown – and not enough
Above all, however, it may have been the pandemic that broke their marriage. As with all families, it transformed the Gates' life. Global travel, the backbone of their, often separate, working lives, was curtailed. Bill and Melinda, like husbands and wives around the world, found themselves marooned with one another.
And as they faced each other at home, the issue that had run like a thread through their marriage will have become inescapable: time. Could Bill – a man some say divides his day into five-minute segments the better not to waste a second – devote time enough to his family?
It was a question that had dogged the couple from the beginning. A couple of weeks after they met, sitting next to each other at a business dinner ("I could sense he was interested") they bumped into each other in the company car park and, according to her "he struck up a conversation and asked me out two weeks from Friday".
A fortnight's wait – how romantic. Melinda gave him her number and demanded more spontaneity. A couple of hours later he rang to ask her out the very same evening with the line: "Is this spontaneous enough for you?"
After dating for seven years it was, he recalled, decision time: "There were only two possibilities: either, we were going to break up or we were going to get married."
Bill was tormented – not because he didn't love Melinda, but because he was unsure he could commit enough time to his family: "When he was having trouble making the decision about getting married, he was incredibly clear that it was not about me, it was about 'Can I get the balance right between work and family life?'"
So, like the methodical man he remains, Gates famously drew a line down a whiteboard, dividing it into two halves: the pros and cons of getting married. Melinda walked in to find him, in his bedroom, totting up the list.
In the end, of course, the couple went for it. But the tension of time, for a man on a mission to make the very most of and do the very best with his power and fortune in the rest of his life, has never gone away.
They have done the things that over-stretched couples do – scheduling fun, rather than having it spontaneously, as Melinda initially demanded. "We've learned how to communicate well with one another," she said.
"Sometimes you've just got to go out and play: doing something fun together; going out to a movie together; going on a date night.
"We are very purposeful about it," she noted. "We lead incredibly busy lives with work and three children so we literally put date nights on our calendar to make sure we do things together."
Even when she realised she was pregnant she "considered not telling Bill" because the couple were about to go away together on a rare holiday. "The trip was a huge deal for us. Bill rarely took time off from Microsoft and I didn't want to mess up the trip."
Two years ago, asked the secret of their quarter-century marriage, she answered unambiguously: "I have learned it takes time."
But during lockdown, though together in person, his mind must have been elsewhere, consumed as he was by the crisis, notably on the vaccine rollout. His wandering attention, easily overlooked during foreign trips, may have become impossible to ignore. In the past year, faced with one of the world's greatest post-war problems, his mind clearly whirred into action as never before.
Could Melinda compete with Covid? No one but the two of them will truly know, but it is interesting to remember the story that goes with that famous picture of him cutting their wedding cake.
While she throws back her head and laughs, a portrait of unbridled joy, her "heart full", as she later said, her husband's mind turned out to be elsewhere, plotting and totting as always.
While she was focused on their life together, he was calculating, doing "some astonishingly quick math", as she later recounted, to cut the cake so that all their guests received an equitable slice.
The story of Bill and Melinda's relationship
• An empire builds: Bill Gates co-founded Microsoft with childhood friend Paul Allen in 1975. Though they looked decades apart, Gates, who has always been boyish, was actually only three years younger. By 1981, Gates had become president and chairman of the board. Allen left the company two years later, after receiving a Hodgkin lymphoma diagnosis. He died in 2018.
• A courtside courtship: After Melinda French was hired by Microsoft as a product manager in 1987, she met Gates at a business dinner. He asked her out (and she turned him down) in the company car park. But by 1993, they were engaged and, as Gates became one of the world's most famous men, went public.
• Jet-setting (within reason): The Gateses married on the Hawaiian island of Lanai on New Year's Day in 1994, and began a relationship remarkable for its wealth, but never ostentatiously so. Holidays weren't glitzy, their wardrobes were almost impressively bad, and a devotion to philanthropy was established early, before they set up the Bill & Melinda Gates Foundation in 2000.
• Making a home: While they were certainly well-grounded and charitable from the get-go, they didn't live like paupers. The couple commissioned a US$60m home in Medina, on the eastern shore of Lake Washington, in 1995. It became known as Xanadu 2.0 in reference to Citizen Kane.
• Breaking new ground: The pair quickly made clear that when it came to philanthropy, they'd be doing things together. Melinda was often seen as cool, calm and firm; Bill more the hapless, ingenious geek. And it worked.
• Fighting malaria: One of the first, and most enduring, shared goals of the Gateses was to do all they could to fight malaria. In 2003 they announced three grants totalling US$168m to fight the disease, and frequently visited research centres to see their work in action.
• A growing legacy: Between their work and charity commitments, the couple still found time to have three children: Jennifer, born in 1996, Rory, born in 1999, and Phoebe, born in 2002. In raising them, Bill and Melinda were strict about technology and luxuries, and the children will only receive a "miniscule portion" of their father's wealth.
• A lifetime's work: In recent years, Bill and Melinda Gates have come to seem more like retired world leaders than mere philanthropists, such is their impact on whatever area they direct their focus and funds towards. In 2017, their work was recognised with the Commander of the Legion of Honour by French President Francois Hollande.
Other big Silicon Valley splits – and settlements
Jeff Bezos and McKenzie Scott
The Amazon founder and world's richest man was married to novelist MacKenzie Scott for more than 25 years, with whom he had four children, before they announced their divorce in 2019. Though the split may have been messy – coming after US tabloids published text messages and private photographs between Bezos and TV anchor Lauren Sánchez – the settlement itself seemed smooth.
MacKenzie was awarded a 4 per cent stake in Amazon (now worth about US$62b) but gave her ex voting control over her shares, and also relinquished her interests in the Washington Post and the Blue Origin aerospace company to him. A month after the divorce she signed up to the Giving Pledge, and last year donated US$6b to causes around the world.
Mark Pincus and Alison Gelb Pincus
Pre-nups aren't always involved in mammoth Silicon Valley divorces – chiefly because many such marriages start before any millions are made, as with Bezos and Gates. Even when they are present, though, they don't guarantee a smooth divorce.
Mark Pincus, an early investor in Facebook and Twitter who is worth US$1.6b, separated from his wife, Alison Gelb Pincus, the co-founder of home decor business One Kings Lane, in 2017 after nine years of marriage.
Pincus founded Zynga, the company behind the game FarmVille, a year before the couple wed, but it grew into a billion-dollar company within four years. There was a prenup, but given most of Pincus's wealth was accrued during the marriage, his ex-wife legally challenged it in court. The final terms of their divorce aren't public, so it's not known if she was successful.
Elon Musk and Justine Wilson
The mercurial Tesla founder has a predictably complicated personal life. He was married to Canadian Justine Wilson for eight years, then filed for divorce, and became engaged to British actress Talulah Riley six weeks later.
He married Riley, divorced Riley, remarried Riley, then divorced Riley again. He's now with pop star Grimes. Seven children have arrived along the way.
Wilson was, in her own words, Musk's "starter wife", and their messy divorce racked up US$4m in legal and accounting fees as the pair took regular shots at one another in the newspapers. If you thought that was expensive, Musk's divorce from Riley reportedly cost him a further US$20m settlement.
Sergey Brin and Anne Wojcicki
If there's a relatively tidy way to do it, perhaps Google co-founder Sergey Brin, who is worth around US$99b, found it.
After eight years married to Anne Wojcicki, founder of 23andMe, his 2015 divorce was settled with little noise, and his Google stake unchanged, thanks to a pre-nup – the details of which haven't been disclosed.
"It's complicated, that's all I can say," Wojcicki told Bloomberg at the time. That may be, but it's not as complicated as others.
- Guy Kelly