President Donald Trump on Thursday, Nov. 7, called for Hunter Biden and his father, former Vice President Joe Biden, to testify after a Republican senator questioned about Hunter’s business dealings.

President Trump repeated a “very good question” from Sen. John Kennedy (R-La.) who asked what Hunter did to earn money.

“What did Hunter Biden do for the money?” @SenJohnKennedy. A very good question. He and Sleepy Joe must testify!” President Trump tweeted.

President Trump and his Republican allies have been questioning how Hunter was qualified to sit on the board of Ukrainian natural gas giant Burisma Holdings while his father was carrying out U.S. policy against corruption in Ukraine.

In a “congratulatory” phone call with Ukrainian new President Volodymyr Zelensky on July 25, President Trump mentioned the corruption situation in Ukraine and asked if Zelensky could “look into” allegations of wrongdoing against Joe Biden and his son.

An anonymous whistleblower filed a complaint on Aug. 12 alleging that President Trump pressured Ukrainian leader to investigate the former vice president. Based on the allegations, House Democrats kicked off an impeachment inquiry against President Trump.

Democrat-led House committees announced they will hold the first public hearings related to the impeachment inquiry next week, but the Bidens are out of their list.

According to The Hill, House Republicans have the power to request a subpoena of witnesses, but their requests are subject to approval by Democrats leading the investigation.

However, the Republican-controlled Senate may call the Bidens to testify as some senators, including Kennedy and Rand Paul, have reportedly suggested the testimony.

Hunter joined Burisma in 2014. The gas company’s founder was under investigation by prosecutor general Viktor Shokin, who the Obama administration and other Western governments argued had failed to rein in corruption in Ukraine. Joe Biden, then U.S. vice president, threatened to withhold roughly $1 billion in loan guarantees if Shokin was not replaced.

In an interview with Fox News earlier this week, the Senate Judiciary Committee Chairman Lindsey Graham has raised a question about the Bidens.

“We need to look at whether or not Hunter Biden corruptly engaged in lobbying, did Joe Biden asked the prosecutor to be fired because he was investigating his son?” Graham said on Nov. 4.