Now that the 47th Vice President of the US has left the White House, many have been wondering: What happened to Joe Biden's first wife Neilia Biden?

Joe, 74, was married to Neilia from 1966 until her death in 1972. Neilia — who was just 30 at the time of her passing — was killed in a car crash on her way to buy a Christmas tree. Her station was whacked by a tractor-trailer as she pulled out from an intersection. The truck driver, unfortunately, did not get charged with any wrongdoings. Their daughter, Naomi, also died in the collision. She was just 13-months-old.

The couple additionally had two sons together, Hunter, 47, and Beau, who sadly succumbed to brain cancer in May 2015. The boys — who were nearly three and four-years-old at the time — were also in the car crash with Naomi and Neilla, and ended up spending months in the hospital.

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Joe and Beau in 2008.

The accident occurred just six weeks after Joe was elected senator. At the time of his son Beau's passing, Joe opened up about the unimaginable tragedy he endured nearly 45 years ago.

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"Six weeks after my election, my whole world was altered forever. While I was in Washington hiring staff, I got a phone call. My wife and three children were Christmas shopping, a tractor trailer broadsided them and killed my wife and killed my daughter. And they weren’t sure that my sons would live," he said during his Yale commencement speech.

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When his son's fully recovered from their injuries, he commuted from their home in Delaware to Washington DC on Amtrak every day. He earned the nickname "Amtrak Joe," considering he did that for 36 years.

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Five years after his wife's untimely death, Joe remarried to Jill Biden, and the two have been together ever since. They're parents to a 35-year-old daughter, Ashley.