In December 1972, Joe Biden's life was picture perfect.

At 30 years old, he had just been elected to represent Delaware in Congress, making him the second youngest senator in history.

He had a beautiful wife of six years, Neilia. They shared three healthy children – sons Beau, 4, Hunter, 3, and 13-month-old daughter Naomi.

In fact, their good fortune was so great that Biden's young wife admitted it made her nervous.  

Sitting by the fire in their Wilmington home writing Christmas cards together, she turned to him, filled with dread.

'What's going to happen, Joey?' she asked. 'Things are too good.'

Days later, newly-elected Biden was working in Washington DC, interviewing prospective staff, when the phone rang.

'They put a pretty young woman on the phone. She was so nervous,' Biden recalled nearly 50 years later at a rally for his 2020 presidential campaign, 'She said: "You gotta come home. There's been an accident."'

At approximately 2.30 pm on Monday, December 18, Neilia had been driving along a suburban road with her three children on the way to pick up a Christmas tree in Hockessin, Delaware, when she crept through a stop sign directly into the path of a speeding tractor-trailer.

Her Chevrolet station wagon was struck side-on and hurled 150 feet into an embankment.

'Biden For Senate' campaign flyers that were still piled in the car's trunk filled the air and were strewn all over the roadway, along with shards of glass and twisted debris.

Neilia, also 30, and Naomi were rushed to Wilmington General Hospital, but it was too late.

They were declared dead on arrival.

Beau and Hunter were severely injured, but alive. Beau's leg had been broken. Hunter's skull had been fractured.

In that instant, Biden became a widower and a single father with two boys under the age of five.

He fell into a state of deep grief and depression, later revealing he even contemplated suicide.

'I thought about what it would be like just to go to the Delaware Memorial Bridge and just jump off and end it all,' Biden told CNN for a 2020 documentary about his political life.

By all accounts, Neilia was a great love.

They had met in 1963, both aged 20, while Biden was on Spring Break in Fort Lauderdale. 

He and his friends were bored and decided to take an impromptu trip to Nassau, where Neilia was holidaying. 

Neilia's wealthy Republican parents were staying at a fancy beach resort that Biden, who grew up the son of working-class parents, could never afford. But he and his pals had stolen towels with the hotel logo and bluffed their way into the resort pool.

Spotting Neilia, Biden said it was love at first sight; but he had competition, as his friends fancied her too. So, they flipped a coin to decide who got to speak to her.

Biden won.

He took Neilia for dinner that night and told her he was going to marry her. Three years later, they wed.

He was infatuated, describing her in a 1974 interview as 'my very best friend, my greatest ally, my sensuous lover.'

After her death, he considered resigning from public office to focus on raising his boys but Senate Majority Leader Mike Mansfield persuaded him not to.

Two and a half weeks after the crash, a media circus descended on the hospital where Hunter and Beau were still being treated for their injuries.

Beau was wheeled into the small chapel attached to the hospital and Hunter was perched on the side of the bed as their father was officially sworn in as senator.

Photos of the ceremony, showing Biden solemnly raising his hand to take the oath with his sickly children in the foreground, were shown around the world.

As he left the hospital, his mother, Catherine Eugenia 'Jean' Biden, turned to him and said: 'Out of everything terrible that happens to you, something good will come if you look hard enough for it.'

But he'd have to wait a while. In the coming months, he went through the motions at work and, instead of moving to Washington, started commuting – two hours each way – from his home in Wilmington.

'I did it because I wanted to be able to kiss [Beau and Hunter] goodnight and kiss them in the morning the next day,' Biden said. Eventually, his sister Valerie moved into the Wilmington home to help care for the young boys.

Meanwhile, Biden's depression worsened. He wrote in his 2017 autobiography that 'it felt like there was a tiny dark hole in the middle of my chest [that] threatened to suck my entire being down into it.'

He started to score his moods on a scale from one to 10, recording them daily on a calendar in the hope of feeling better.

The number one signified he felt like he was having the worst day of his life, ten signified the best day. For six months, he filled the calendar with ones.

It wasn't until three years after Neilia and Naomi's deaths that life began to turn around for Joe, 32, when he was set up on a blind date with Jill Jacobs, 23.

Biden would later say: 'No man deserves one great love, let alone two.'

In 1977, Joe and Jill married. Four years later, they welcomed their first and only child, Ashley.

But more family tragedy came in 2015, when Joe's son Beau died of brain cancer aged 46.

As a result, 'many voters see Joe Biden primarily through the prism of his history of loss,' Biden biographer Ben Schreckinger told DailyMail.com. 

'In many ways, he shaped his political identity around his grief using his personal experience to help him empathize with the public and colleagues on the Hill.

'In political circles, he is known for reaching out personally to console people, whether or not they are his political allies, who have lost loved ones.'

But not everyone has received such empathetic treatment.

The driver of the truck that smashed into the Biden family car, Curtis Dunn, then 33, escaped unscathed and was absolved of all wrongdoing when police determined that Neilia had accidentally driven into his path.

Investigators also found that Dunn had attempted to avoid the collision with such force that he'd overturned his rig, before then rushing to help Neilia and the children.

But in the decades following, Biden has repeatedly and falsely implied that Dunn was at fault and had been drinking, describing him as 'a guy who allegedly – and I never pursued it – drank his lunch instead of eating his lunch.'

In 2009, Dunn's daughter Pamela Hamill was asked about Biden's claims for a CBS News report.

Her father had passed away in 1999, but Pamela said she had been so upset that she had asked Biden for an apology.

Later, she admitted he had, privately at least, been 'very apologetic', calling her personally. But, she said, he'd drawn the line at issuing a 'public apology', saying if he did it would 'end up in all the trashy magazines in the grocery store.'

Hamill never took Biden up on an offer to meet with her family in person, and she never heard from him again.

As the 81-year-old president now prepares to step back from politics, announcing Sunday that he would no longer accept the Democratic nomination to run again in November's general election, it seems unlikely that Hamill will ever see the record corrected.