House Republicans have subpoenaed US President Joe Biden's son, Hunter Biden, and brother, James Biden, to appear for depositions, in an escalation of its impeachment inquiry into the Democrat.
The Republican-controlled House oversight committee launched an impeachment inquiry in September, following months of probes.
They allege that Biden and his family have personally profited from policy decisions made by Biden when he was vice-president during president Barack Obama's administration.
James Biden could not immediately be reached for comment.
Abbe Lowell, Hunter Biden's lawyer, called the subpoena "yet another political stunt".
"Nevertheless, Hunter is eager to have the opportunity, in a public forum and at the right time, to discuss these matters with the Committee," Lowell said in a statement.
Devon Archer, a former business associate of Hunter Biden, told the House oversight committee earlier this year that the younger Biden sought to create "an illusion of access to his father" and put his father on the phone with foreign associates "maybe 20 times" over the course of Archer's business relationship with Hunter Biden.
White House press secretary Karine Jean-Pierre on Wednesday called the investigation a "smear campaign."
The investigation "has gone on for a year now and has turned up zero evidence against the president", she said.
The impeachment inquiry has been publicly supported by former president Donald Trump, who is the frontrunner for the Republican nomination to take on Biden in the 2024 election.
The committee has also issued a subpoena to Rob Walker, a former business partner of Hunter Biden, and said it would send additional subpoenas and interview requests later in the week.
The committee held a public hearing related to the inquiry in September, which was a review of material related to foreign business ventures by Hunter Biden, which Republicans say indicate the president's family members were selling access.
Hunter Biden, 53, has publicly discussed his past substance abuse and never held a position in the White House or on his father's campaign.
Trump was the first US president to be impeached twice. He was acquitted by the Senate both times. Trump is facing four criminal indictments related to his business activities, alleged mishandling of classified documents and alleged attempts to overturn the 2020 election.
It is not clear if the full House of Representatives, controlled by a narrow Republican majority, would vote to impeach Biden, though Speaker Mike Johnson has supported the probe.