Bill Gates was asked to step down from Microsoft's board in 2020 as board members pursued an investigation into the billionaire’s romantic relationship with a female Microsoft employee.

The alleged affair is with an unnamed Microsoft engineer, who disclosed her relationship with him in a letter. 

These were revealed as Gates and his wife, Melinda, are undergoing divorce settlement.

Microsoft board members hired a law firm to investigate the woman's allegations and deemed the relationship inappropriate, and by early 2020 "some board members decided it was no longer suitable for Mr. Gates to sit as a director at the software company he started and led for decades," the Journal reports. 

Mr. Gates resigned before the board’s investigation was completed and before the full board could make a formal decision on the matter, another person familiar with the matter said.

In a press release filed with regulators and a post on LinkedIn, the billionaire said then he wanted to focus on his philanthropy and would continue to serve as a technical adviser to Chief Executive Satya Nadella. 

That same day, he also vacated his board seat at Berkshire Hathaway Inc., the conglomerate run by Mr. Gates’s friend Warren Buffett.

Melinda Gates had been upset with her future ex-husband on and off for years. 

"In some circles, Bill Gates had also developed a reputation for questionable conduct in work-related settings," and on at least a few occasions he had "pursued women who worked for him at Microsoft and the Bill and Melinda Gates Foundation."

"It is not clear how much Ms. French Gates knew about her husband's behavior or to what degree it contributed to their split," the Times reports.

Mr. Gates, 65 years old, and his wife Melinda French Gates, 56, announced earlier this month that they were ending their marriage after 27 years. 

In a joint statement posted on Twitter, the couple said, “We no longer believe we can grow together as a couple in this next phase of our lives.”