Robert Mueller has been battling Parkinson’s disease for four years and is experiencing difficulty speaking, his family has revealed.

The revelation came after House Oversight Committee Chairman James Comer subpoenaed Mueller to testify in an inquiry into the Jeffrey Epstein case, as part of his former role as FBI director from 2001 to 2013.

Mueller’s family revealed on Sunday that the 81-year-old had actually been diagnosed with the degenerative neurological disorder in the summer of 2021. Mueller served as special counsel in 2017 to determine if the Russian government interfered with Donald Trump’s first campaign for president.

Special Counsel Robert Mueller makes a statement about the Russia investigation on May 29, 2019 at the Justice Department in Washington, DC. Chip Somodevilla/Getty Images

“He retired from the practice of law at the end of that year,” the family said in a statement to The New York Times. “He taught at his law school alma mater during the fall of both 2021 and 2022, and he retired at the end of 2022.”

They asked that Mueller’s privacy be respected.

Mueller has experienced difficulty speaking and with mobility, according to the Times.

Lawmakers withdrew their request for him to take part in the Epstein inquiry after learning that Mueller had “health issues that preclude him from being able to testify,” a source familiar told Fox News Digital.

The former FBI director was due to appear on Tuesday as part of broader investigations into the Epstein files. A letter Comer sent to Mueller on Aug. 5 read, “Because you were FBI director during the time when Mr. Epstein was under investigation by the FBI, the committee believes that you possess knowledge and information relevant to its investigation,” according to ABC.

Former Special Counsel Robert Mueller was diagnosed with Parkinson’s disease four years ago. Alex Wong/Getty Images

After being nominated by George W. Bush, Mueller became the sixth director of the FBI on Sept. 4, 2001, and held the position until 2013, overseeing the bureau during its original investigation of disgraced financier Epstein in 2006.

In June 2008, Epstein was sentenced to 18 months in a minimum-security facility after striking a deal with federal prosecutors to plead guilty to state charges of solicitation of prostitution and of solicitation of prostitution with a minor under the age of 18.

He was released in 2009 and was arrested in July 2019 on one count of sex trafficking of minors and one count of conspiracy to commit sex trafficking of minors. He was found dead in jail in August 2019.

FBI Director Robert Mueller speaks during a news conference at the FBI headquarters June 25, 2008 in Washington, DC. Alex Wong/Getty Images

As part of his investigations into Russian interference in the 2016 election, Mueller did not establish collusion between Trump and Moscow, but he could not clear him. “The president was not exculpated for the acts that he allegedly committed,” Mueller said at the time.

The investigations led to criminal charges against 37 defendants, including six Trump associates. Former Trump lawyer Michael Cohen pleaded guilty to charges including lying to Congress about efforts to build a Trump Tower in Russia during the campaign.