Microsoft (MSFT) co-founder Bill Gates and his wife, Melinda, will separate after 27 years together, the billionaire announced on Monday, ending a marriage that launched an influential globe-spanning philanthropic and humanitarian empire.

Via Twitter, Gates — one of the world's wealthiest people — said that he and his wife remain committed to their "mission" as philanthropists, but "we no longer believe we can grow together as a couple in this next phase of our lives."

The philanthropic organization that bears both their names has an endowment of nearly $50 billion, and in 2019 doled out around $6 billion to various causes, according to its most recent annual report. Since its inception, the foundation has paid out almost $55 billion in grants.

The tech titan, who emerged as a leading voice in the fight against COVID-19 and frequently weighs in on matters impacting the environment and public health, currently sits at number four on Forbes' list of the wealthiest people, with an estimated net worth of over $130 billion as of Monday.

Melinda Gates, a graduate of Duke University, worked as a general manager at Microsoft — having been recruited just after the company went public.

[See also: Bill and Melinda Gates already decided how to divide wealth: 'Divorce is not something to waste money on']

The couple jointly chairs one of the world's largest philanthropies, and both are signatories of Warren Buffett's Giving Pledge, a commitment of the world's wealthiest people to donate the majority of their wealth to philanthropic endeavors. Buffett and Gates have been close friends for nearly 30 years, with the latter crediting the former for having taught him important lessons on life and investing.

According to multiple sources, Gates foundation staff was alerted ahead of time before the couple broke the news on social media — with one staffer describing the internal mood as one of "total shock."

The Gates' divorce raises questions about how one of the world's largest fortunes will be divided, but Amazon (AMZN) founder Jeff Bezos provides a useful test case of how the fruits of the Gates' union will be divided.

Bezos' split from ex-wife Mackenzie Scott resulted in the latter instantly becoming the one of the wealthiest women in the world. Since then, Amazon's surging stock has landed Bezos right back on top the billionaire's league tables.