Biden said he always had feelings of loneliness and not fitting in.
"I am more convinced now that trauma is at the center of it," Biden said, noting that while he and his father and brother talked about his late mother all the time, they never discussed the car accident that killed her and his sister or "the darkness" that his dad went through afterward.
"I think there's a lot of research now that almost all addicts who suffer from addiction have serious trauma in their lives," he said.
The affair with his brother's widow
After Beau Biden died of brain cancer in 2015, Hunter Biden — at that point separated from his first wife, Kathleen — turned to his brother's widow, Hallie Biden. Their affair cost Hunter clients and other business relationships.
"I think people were confused by it, and I understand that. I mean, I really do. To me it's not something that is difficult to explain, because it came out of a real, overwhelming grief that we both shared," he said.
"That grief turned into a hope for a love that maybe could replace what we'd lost," Biden said. "And it didn't work."
Relationship with his father
Turns out the president calls his son every night, right before he goes to bed, and does the same for his grandkids, Hunter's children.
"He's always done that. ... Because he, like me, knows what it's like not to be able to pick up the phone and talk to his son," Hunter said. Interviewer Tracy Smith then reminded him that the president "almost lost you." The camera lingered on Biden as he eyes turned red and he began to tear up.