Divorce, on paper, seems quite common: the years go by, the children grow up, the couple separate. The marriage, they finally say to a court, has become “irreparably broken.”

But that’s where the familiar outlines of many breakups end, because this one is about Bill and Melinda Gates.

In financial terms, it’s a split for the ages. Unraveling their common fortune after 27 years of marriage is a colossal undertaking.

There are mansions, private jets, large tracts of land, a hotel brand, and massive investments in public and private companies.

Then there’s the Bill & Melinda Gates Foundation – the largest such philanthropic organization on the planet.

“This is probably the biggest divorce imaginable,” said Janet George, family lawyer with McKinley Irvin in Washington.

Work has already started, starting with a separation contract, according to Ms Gates, 56, filed for divorce in their long-standing home state of Washington.

She signed the Bellevue papers, where they have a $ 130 million lakefront mansion. Mr. Gates, 65, signed from Palm Desert, Southern California, where they own another home.

Representatives for the couple declined to comment on the divorce and whether they had a prenuptial agreement.

But a marriage contract, if there is one, would not matter, as the separation contract supersedes any previous agreement.

There have already been over $ 3 billion in transfers from Cascade Investment, also known as BMGI (Bill and Melinda Gates Investments), to Ms Gates, a fraction of their $ 145 billion fortune at the time of the divorce announcement.

So far, there is no clear pattern as to how stocks are divided.

The 2.25 million Deere & Company shares Ms Gates received are worth around $ 800 million, but they were only 7% of the estranged couple’s total stake in the business.

During this time, she received all of the company’s shares in Coca-Cola Femsa, a Mexican distributor, worth around $ 130 million.

We may never make public what is happening with their collection of private companies, like the Four Seasons brand in which they bought a 47.5% stake in 2007 with Saudi Prince Al Waleed bin Talal.

Or their real estate investments, which make them the largest owner of private farmland in the United States.

Although not part of their fortunes, one of the couple’s biggest assets is their foundation, which has $ 50 billion in assets, more than 1,600 employees and offices around the world.

Their philanthropy has particularly transformed Mr. Gates’ reputation – from the monopoly capitalist behind Microsoft to the tech-geek benefactor fighting global hunger and health.

Divorce has already cost Mr Gates some of that picture, with reports of infidelity, ties to Jeffrey Epstein and reports that his fund manager Michael Larson was exploiting a toxic work environment.

The couple have established their own philanthropic branches outside of the foundation and their interests have diverged in recent years, with Mr Gates focusing on climate change and Ms Gates on gender equality.

For the career philanthropists they have become, this means how the way wealth is distributed will determine where funds go to these causes for decades to come.