Hunter Biden, the only living son of President Joe Biden, is attracting attention once again.
The Justice Department has appointed a special counsel, David Weiss, to investigate him.
The announcement came weeks after a plea deal on tax and gun charges against Hunter Biden fell apart.
The younger Mr Biden – a long-time target of Republican criticism – has been under federal investigation since 2019.
The special counsel appointment has not silenced his critics, however.
Former President Donald Trump and his allies have long alleged that the 53-year-old is guilty of widespread corruption, particularly in his foreign business dealings in China and Ukraine.
- Hunter Biden charged with tax and gun offences
President Biden, meanwhile, has stood by him through his public and private struggles.
The White House has said that the "President and First Lady love their son and support him as he continues to rebuild his life".
Hunter Biden had initially reached a deal with prosecutors to plead guilty to two misdemeanour tax crimes and admit to illegally possessing a gun while a drug user. The terms of the agreement likely would have kept him out of jail.
But last month, a judge said she could not sign off on the deal due to "non standard terms" and the "unusual" nature of the proposed resolution for the gun charge.
The younger Biden's well-documented personal travails, including a public marital break-up and drug addiction – have spilled over into politics since his father entered the White House.
But what more do we know about Hunter Biden?
A childhood forged by tragedy
Born in Wilmington, Delaware, in 1970 to President Biden and his first wife Neilia Biden, Hunter was given his mother's maiden name as his first name.
He was only two years old in December 1972 when – less than six weeks after his father's election to the US Senate – a truck rammed into the family car and took the lives of his mother and his baby sister Naomi.
The accident left him with a fractured skull and his older brother Beau with a broken leg. The elder Mr Biden – who was not in the car – took his oath of office from their hospital room.
Image source, Getty ImagesImage caption, Hunter (extreme left) looks on with his family after Joe Biden announces his first run for the presidency in 1988
Hunter later attended Georgetown University and Yale Law School, graduating in 1996.
Between the two degrees, he joined the Jesuit Volunteer Corps, a Catholic group that volunteers to serve marginalised communities.
There, he met his first wife, Kathleen Buhle, a lawyer, and they wed in 1993.
They have three children – Naomi, Finnegan and Maisy – but the pair split in 2017.
The 'darkness' of addiction
His father is teetotal, but Hunter started drinking as a teenager and confessed to abusing cocaine as a college student.
He has been in and out of rehab.
In 2013, he signed up for the US Navy Reserves and took the oath of office before his father – then the vice-president – in a White House ceremony. But on his very first day at the naval base, he tested positive for cocaine use and was discharged, something he later said he was "embarrassed" by.
According to the New Yorker, he drank excessively after the death of his older brother, Beau, from brain cancer in 2015, sometimes only leaving the house to buy vodka.
"He and Beau were one," his daughter Naomi once wrote on Twitter. "One heart, one soul, one mind."
During an acrimonious divorce filing in 2017, Ms Buhle accused Hunter of "spending extravagantly on his own interests (including drugs, alcohol, prostitutes, strip clubs, and gifts for women with whom he has sexual relations) while leaving the family with no funds to pay legitimate bills".
Breaking her silence last year on how their 24-year marriage unravelled, Ms Buhle told Good Morning America: "He was struggling under a massive drug addiction, and that's heart-breaking and painful and that wasn't who I was married to."
Image source, Getty ImagesImage caption, Hunter (extreme left) walks with his then-wife Kathleen, father Joe and step-mother Jill in 2009
In his 2021 memoir Beautiful Things, Hunter confesses that his infidelity to Ms Buhle was the final straw in their marriage.
A DNA test in 2019 found he was "the biological and legal father" of a child born to an exotic dancer, Lunden Alexis Roberts.
Hunter claimed to have "no recollection" of their encounter in his memoir. But he has settled a paternity suit with Ms Roberts and now pays her child support.
And before his split from Ms Buhle was finalised, Hunter began a relationship with his brother's widow, Hallie Biden, for two years, bonding over the shared and "very specific grief" of their loss, he told The New Yorker.
Mere weeks later, Hunter wed South African filmmaker Melissa Cohen after a whirlwind six-day romance. They have one son.
Speaking out in 2019 on his struggle with addiction, he said: "You don't get rid of it. You figure out how to deal with it."
In Beautiful Things, he credits his survival to his family's love, recounting an intervention when his father held him in an embrace, saying: "I don't know what else to do. I'm so scared. Tell me what to do."
The New York Times reported that he had turned to painting as a form of therapy, quoting him as saying that it "keeps me away from people and places where I shouldn't be".
But a 2021 art exhibition to sell his paintings – for up to $500,000 a piece – created an ethics dilemma for the Biden White House.
Mixing family and business
After graduating from Yale Law School, Hunter worked at MBNA America, a bank holding company headquartered in Delaware and later acquired by Bank of America.
- What was Hunter Biden doing in Ukraine and China?
However, his father's close relationship with the bank – one of the largest employers in Delaware and a top contributor to his political campaigns – earned him the unfavourable moniker of "the senator from MBNA". As the younger Mr Biden rose to the rank of executive vice-president, his father pushed bankruptcy reform legislation favourable to the bank through the Senate.
In the early 2000s, while still receiving consulting fees from the bank, Hunter opened a Washington lobbying practice that – according to Politico Magazine – saw him land "clients with interests that overlapped with [his father's] committee assignments and legislative priorities".
The father-son relationship at the time, he told The New Yorker, was that neither would speak to the other about lobbying work. President Biden has maintained this to be true in the case of more recent allegations of wrongdoing as well.
Image source, Getty ImagesImage caption, Hunter (left), with father Joe and brother Beau, waves at supporters during Barack Obama's inauguration as president
In 2006, with then-Senator Biden set to re-assume chairmanship of the Senate's Foreign Relations Committee, his son and another relative made an ill-fated purchase of a hedge fund group, Paradigm Global Advisors.
Their tenure at Paradigm extended through Joe Biden's 2008 run for president and selection as vice-president to President Barack Obama. During this time, the fund was connected with several alleged criminal frauds, including a Texas financier convicted of running one of the largest Ponzi schemes in US history. The Bidens denied any wrongdoing and faced no charges. In 2010, they liquidated the fund and returned money to investors.
China and Ukraine
Ex-President Trump and the Republican party have argued that foreign business dealings involving President Biden's son were questionable and had conflicts of interest.
From 2013-16, he held a board seat at the Chinese private equity firm BHR Partners, first as an unpaid member and later owning a 10% equity stake in the fund.
Mr Trump, who has insisted Joe Biden is "China's puppet", repeatedly pointed to this position as alleged evidence of his rival's corruption.
After his father left the White House in 2017, Hunter partnered with Chinese billionaire Ye Jianming – an oil tycoon – on a natural gas project in Louisiana. The deal appears to have collapsed after Ye was detained by Chinese authorities on corruption charges and subsequently went missing.
But it has been business dealings in Ukraine that have stoked the most controversy.
In 2014, Hunter joined the board of a Ukrainian natural gas company, Burisma Holdings, where he was reportedly paid up to $50,000 (£38,000) per month.
At the time, his father was actively engaged in anti-corruption work in Ukraine. Vice-President Biden rallied other Western leaders to call for the firing of the country's top prosecutor, Viktor Shokin, who faced criticism for blocking corruption investigations.
Mr Shokin was removed by the Ukrainian parliament in 2016. Mr Trump and some of his allies have claimed he was ousted for investigating Burisma.
House Republicans have alleged that both Joe and Hunter Biden received payments of $5m from Burisma executives in exchange for getting Mr Shokin fired.
They have based those claims on an FBI document known as an FD-1023, which is used by agents to record tips from confidential sources. President Biden called the allegations "a load of malarkey."
Allegations of corruption by the Bidens formed the centrepiece of the campaign to impeach President Trump in 2019, after he pressured Ukrainian President Volodymyr Zelensky in a telephone call to investigate Hunter's dealings with Burisma.
He has since resigned from the boards of both BHR Partners and Burisma Holdings.
Image source, Getty ImagesImage caption, Hunter (left) and sister Ashley wave as they arrive at their father's presidential inauguration
During the 2020 election campaign, it emerged that a laptop the younger Mr Biden abandoned at a repair shop contained a 2015 email in which a Burisma adviser thanked him for the invitation to meet his father, then the US vice-president, in Washington DC.
Without providing evidence, the elder Mr Biden called the allegations a "smear campaign" engineered by Russian disinformation.
And though the email has since been authenticated, his representatives have repeatedly denied such a meeting ever took place, adding that Joe Biden had never discussed going into business with his relatives.
The FBI reportedly seized the laptop from the repair shop and its contents were examined as part of the federal investigation into Hunter Biden.
An NBC News analysis concluded that Hunter's firm brought in about $11m (£9.2m) through its work in Ukraine and China from 2013-18, including nearly $5m from the Louisiana gas venture alone.
It also reportedly revealed spending of more than $200,000 a month at one point on luxury hotel suites, sports car payments and cash withdrawals, among other expenditures.
Congressional Republicans are also looking into reports that a wealthy Hollywood lawyer has loaned $2m to help Hunter pay off his back taxes, CBS reported this year.
President Biden has defended Hunter on multiple occasions.
During a presidential debate in the last election, Mr Trump savaged his opponent: "Hunter got thrown out of the military, dishonourably discharged for cocaine use, and he didn't have a job until you became vice-president."
An emotional Joe Biden responded: "That is simply not true. My son – like a lot of people – had a drug problem. He's fixed it and worked on it, and I'm proud of my son."