A Democratic senator agreed that Hunter Biden could be called to testify during President Trump’s Senate impeachment trial.

Sen. Sherrod Brown of Ohio appeared on CNN's State of the Union on Sunday to talk about the trial days after Chief Justice John Roberts swore in every senator as a juror. Brown, 67, told CNN host Brianna Keilar that Biden, son of former Vice President Joe Biden, may be called to testify if Democrats succeed in securing their requested witnesses, such as former national security adviser John Bolton.

"Fine. I think you bring in — we take the position that we want to hear from witnesses," Brown said. "I don’t know what Hunter Biden has to do with the phone call," but "I understand both sides get to call witnesses."

The House launched an impeachment investigation into Trump after hearing allegations that the president attempted to use foreign aid to Ukraine to push Ukrainian President Volodymyr Zelensky to investigate Joe Biden in a July 25, 2019 phone call.

Joe Biden, 77, is a front-runner in the Democratic primary to challenge Trump for office in November. His son’s business dealings in places such as China and Ukraine have brought attention to his tenure in the Obama administration and have led to allegations of corruption and nepotism.

GOP Senate Majority Leader Mitch McConnell is considering a proposal to call Hunter Biden, 49, to testify about how he landed a job on the board of an Ukranian energy company while his father was heading the Obama administration’s agenda in Ukraine. In exchange for Biden’s testimony, Democrats could call Bolton.

The younger Biden has a history of drug use and controversy, including an ongoing paternity case in which an Arkansas woman claimed he is the father of her child. A court-ordered DNA test identified Biden as the father, and he has not contested the results.