A Republican U.S. senator has called for a Senate-level investigation into Donald Trump Jr. and Hunter Biden, the son of former President Joe Biden.

Cointelegraph, a blockchain media outlet, reported on Monday that Utah Senator John Curtis (존 커티스) sent a letter to Senate Judiciary Committee leadership urging a review of whether presidential family relationships were used as channels for private financial gain, preferential treatment or access by domestic and foreign stakeholders.

In the letter to Judiciary Committee Chairman Chuck Grassley and ranking member Dick Durbin, Curtis also asked that subpoenas be issued for Trump Jr. and Hunter Biden. He said the purpose was to establish the facts, assess the applicability of existing ethics, disclosure and anti-corruption laws, and find needed institutional changes so the presidency does not become a means to increase the private wealth of those closest to the president.

In the letter, Curtis specifically took issue with Trump Jr.'s crypto-related activities. He said Trump Jr. actively promoted a family-backed crypto business and served as an adviser to a prediction-market platform overseen by the Commodity Futures Trading Commission. He also cited Trump Jr.'s receipt of a wedding gift from Russian oligarch Umar Kremlev. President Donald Trump said last week he returned the value of the gift his son received. Trump Jr. and his wife had called it a "generous wedding gift."

Curtis cited Hunter Biden's significant business ties with foreign companies as a concern. He argued both men should be investigated to determine whether their relationship to the president was used as a source of value, or was perceived that way. He also noted that Hunter Biden has denied that his father was involved in his business dealings. Former President Joe Biden granted his son a pardon in December 2024, covering crimes he may have committed or participated in over the past 10 years.

Conflict-of-interest controversy around the Trump family's crypto businesses is not new. Until now, Democratic lawmakers have largely called for investigations into Trump's memecoin, the family-linked business World Liberty Financial, and a $500 million deal tied to Abu Dhabi's royal family. This time, a Republican lawmaker has put the same issues at the forefront.

The move came a week after a bill to clarify the digital asset market failed to pass in the Senate after it did not secure enough Democratic votes. Some Democratic lawmakers cited opposition to what they called Trump "turning the presidency into a money-making machine using cryptocurrency." Trump disclosed that he earned $1.4 billion from digital asset-related businesses in 2025.

Republicans said before the vote that Trump agreed to accept stronger ethics provisions related to his own crypto investments. Democrats countered that the measures alone were not enough to prevent the possibility of corruption. The crypto businesses of the president's family and conflict-of-interest concerns have remained key issues in Congress alongside debate over a market-structure bill.