US President Joe Biden's second son, Hunter Biden, stated in December 2020 that he was under federal investigation for "tax problems" relating to his business transactions in Ukraine and China.

According to the New York Post (NYP), Hunter Biden's former girlfriend and textile designer Zoe Kestan has secretly testified before a grand jury in Wilmington, Delaware, in Hunter's tax investigation.

"The newspaper quoted an unnamed source as saying that the 28-year-old lingerie and textile designer was asked on Tuesday about Hunter Biden's whereabouts and spending habits during 2018 when the two were seen attending art-show openings and parties on Manhattan's Lower East Side."

The queries, according to the source, were about which hotels Biden stayed at and whether Kestan knew where his money came from.

The 28-year-old apparently testified about spending time with Biden at a variety of high-end hotels in Manhattan and Los Angeles, including the Four Seasons, Mercer, SIXTY SoHo, and Soho Grand, as well as the Hollywood Roosevelt, NoMad, and celebrity-friendly Chateau Marmont.

"Kestan also claimed that Hunter Biden told her to withdraw "thousands of dollars at a time" from ATMs, giving her cash to buy clothing, meals, and other items. She added that she had no idea how he obtained the money, according to the source.

Kestan also felt "super-crazy" after learning about Hunter Biden's second marriage to Melissa Cohen in the summer of 2019.

According to the source, the designer believes she is responsible for the 52-year-decision old's to stop drinking and pursue a new career as a painter because she was "with him at the craziest point of his life," having told Biden that "art was a great way to see a hopeful future, rather than using drugs."

Hunter Biden recounted his history with heroin addiction in his memoir "Beautiful Things," published in 2021, admitting that he had been in and out of treatment many times over the last two decades.

Hunter Biden investigated over 'Tax Affairs'

Hunter Biden said last year that he is "100%" convinced that he will be "cleared of any wrongdoing" in the Department of Justice (DOJ) investigation into his taxes.

This came after the president's second son confirmed in late 2020 that he is under federal investigation for "tax affairs" related to business dealings in Ukraine and China, according to Fox News. The network claimed that he had failed to report $400,000 in income from the Ukrainian energy company Burisma Holdings.

"I take this matter very seriously but I am confident that a professional and objective review of these matters will demonstrate that I handled my affairs legally and appropriately, including with the benefit of professional tax advisers", the president's son argued in a statement at the time.

The announcement was preceded by a scandal in October 2020, when the New York Times published an article about two emails that the 52-year-old had supposedly received from a top Burisma executive, while serving on the company's board of directors.

Burisma board adviser Vadym Pozharskyi allegedly asked Hunter Biden to "use [his] influence" to help the Ukrainian company gain political support in a May 2014 email, while Pozharskyi thanked the younger Biden for setting up a meeting with his father, then-US Vice President Joe Biden, in an April 2015 email.

The claimed emails were allegedly obtained from the hard disk of a damaged laptop belonging to Hunter Biden that was taken to a shop in his native state of Delaware for repairs.