Biden revealed this week just how deep the bond runs, telling CNN that Obama offered him money during Beau's illness.

Biden told the president that, to make sure he could take care of Beau's family, he and wife Jill might have to sell their house. But Obama wouldn't stand for that.

"He got up and he said, 'Don't sell that house. Promise me you won't sell the house,'" Biden said. "He said, 'I'll give you the money. Whatever you need, I'll give you the money. Don't, Joe -- promise me. Promise me.'"

Watch the emotional moment in the interview above.