With the president now running for a second term in office, Republicans -- particularly Donald Trump -- are accusing father and son with reaping millions of dollars through Hunter's business deals in China and Ukraine.
If some see Hunter, 53, as the family black sheep, his father has stuck by him.
"My son has done nothing wrong. I trust him. I have faith in him," Joe Biden said last month as Republicans in Congress launched a new probe.
- Alcohol and crack -
A graduate of the elite Yale law school, Hunter drifted between jobs in government, banking and lobbying before landing in a family-controlled hedge fund and his own international business consultancy in the late 2000s.
But his life was marred by alcoholism and addiction to crack cocaine and stints in rehabilitation.
Hunter ties his addictions to the car crash that killed his mother and sister when he was three and hospitalized him with a fractured skull.
But he also lived in the shadow of Beau, who had a sterling military career and went into politics, with his father predicting he could become president one day, before being felled by brain cancer in 2015.
After that, at nearly every opportunity Joe spoke of his loss of his son, empathizing with others who had lost children.
Meanwhile Hunter rarely got a mention.
Hunter wrote in his memoir that after Beau's death the drugs only got worse, hitting bottom around the time Joe's vice presidency ended in 2017.
His marriage fell apart and he lost custody of their three daughters.
He had an affair with Beau's widow, had a child with another woman in Arkansas who sued him, and then saw his files, emails and lurid photos from his laptop computer made public by his father's enemies.
And he came under investigation by the Justice Department over millions of dollars he earned from his overseas investments.
But if Joe seemed to favor Beau, he defended Hunter when challenged over him, like during the 2020 presidential race when Trump raised Hunter's drug use and business deals during a debate.
"My son, like a lot people ... had a drug problem,” Joe Biden said on national television.
"He's overtaken it, he's fixed it, he's worked on it. And I'm proud of him. I'm proud of my son," he said.
- 'He never judged me' -
In his 2020 memoir "Beautiful Things," Hunter Biden recounts his days chugging vodka from the bottle, wandering around seedy neighborhoods at night searching for crack, and multiple failed attempts to get clean.
He said that in 2019 he was able to pick himself up after an intervention by his father and his second wife Melissa.
The one thing that helped him, he wrote, was his father's unconditional love.
"He never abandoned me, never shunned me, never judged me, no matter how bad things got," Hunter wrote.
"There were times when his persistence infuriated me -- I'd attempt to fade to black through alcoholism or drug addiction, and then there he was, barging in again with his lantern, shining a light, disrupting my plans to disappear," he said.
Today Hunter says he is clean. He had a son with Melissa, whom he named Beau.
He took up painting, though that brought fresh controversy when unnamed collectors bought his works for prices in the hundreds of thousands of dollars.
Even with the federal case now behind him, questions about his business dealings are not going away as his father is expected to face Trump again in the 2024 presidential election.
Last month Republicans in Congress accused the Biden family of taking in more than $10 million from Hunter's business deals -- though they offered little evidence.
"Hunter Biden and his associates courted business in countries that correlated directly with Joe Biden's work as vice president," said House Oversight Committee Chair James Comer.
Both Bidens deny the charges.
