The younger Biden is at the centre of murky allegations that not only have the potential to topple Mr Trump but also end his own father’s bid to be the Democrat presidential nominee.
It is he who Mr Trump is said to have requested the Ukraine investigate in return for business and military deals with the US.
The younger Biden was on the board of an energy company in the country when it is said his father - then US vice-president - urged the Ukraine government to fire a prosecutor looking into wrong-doing at the firm.
But Mr Trump’s demands that this be investigated came to light when an anonymous whistleblower claimed the president was threatening to withhold military aid to Ukraine if its government did not agree to his demands.
Now, in his letter to Committee Chairman Adam Schiff, House Intelligence Committee Ranking Member Devin Nunes wrote: “Americans see through this sham impeachment process, despite the Democrats' efforts to retroactively legitimise it last week.
“To provide transparency to your otherwise opaque and unfair process, and after consultation with Ranking Member Jim Jordan and Ranking Member Michael McCaul, the American people deserve to hear from the following witnesses in an open setting.”
He added: “Moreover, given the multiple discrepancies between the whistleblower's complaint and the closed-door testimony of the witnesses, it is imperative that the American people hear definitively how the whistleblower developed his or her information, and who else the whistleblower may have fed the information he or she gathered and how that treatment of classified information may have led to the false narrative being perpetrated by the Democrats during this process.”
The letter – leaked to Fox – also showed the Republicans wanted Alexandra Chalupa as a witness.
She was a Ukrainian-American consultant for the Democratic National Committee, who allegedly held meetings with staff at the Ukrainian Embassy in the US.
They claim she is a “prime witness” given Trump's documented belief that the Ukrainian government meddled in the 2016 election to oppose his candidacy.
Also included on the list are Nellie Ohr, a researcher at Fusion GPS, a firm which was paid by Democrats to compile dossier on Trump's Russia ties and which formed the basis of the Mueller investigation into Russian meddling in the 2016 election.