Bill and Melinda Gates announce divorce

Gates' biggest asset is Cascade Investments, a holding company he created with the proceeds of Microsoft stock sales and dividends.

Through Cascade, Gates has interests in real estate, energy and hospitality as well as stakes in dozens of public companies, including Canadian National Railway and tractor-maker Deere and Co, according to Bloomberg.

Last year, Gates also stepped down from the board of Berkshire Hathaway, the conglomerate run by his close friend Warren Buffett.

Buffett has donated billions of dollars to the Gates Foundation over the years and has pledged to leave the majority of his fortune to the foundation when he dies.

In 2010, Buffett and the Gateses created the Giving Pledge, an effort to get wealthy individuals to commit to donate a majority of their money to charitable causes.

Agencies contributed to this story.