The former vice president and his wife have been interviewed by a television network about their son, who died in a car accident in 2011.
The interview will air Sunday on CNN.
Biden said his son had a very tough childhood, saying he was a great student and a great athlete.
But the interview also touches on his other son, Biden’s youngest son Beau, who was diagnosed with brain cancer in 2015.
The vice president said his wife’s support for Beau during his battle with brain tumors made her the best person he could have asked for as a father.
Biden said Beau’s cancer diagnosis was a difficult decision, and that he was proud to be the father of a child who is now healthy.
“He could’ve been the very, very, most dangerous person in the history of the world,” Biden said.