In a never before told story, Vice President Joe Biden revealed that President Barack Obama once offered financial help when his son was ill.

Biden sat down for an interview with CNN, in which he recalled a weekly lunch with the president.

Obama seemed deeply concerned on how Biden and his wife were managing to provide for their son Beau's family. Biden replied that it he "worked it out," and he and Jill were preparing to sell their home in Wilmington, Delaware.

Biden said Obama, who would be "mad" that the story was being told, was extremely opposed to the idea of Biden selling the house. He made him promise not to do so.

"[Obama] said, 'I'll give you the money. Whatever you need, I'll give you the money. Don't, Joe -- promise me. Promise me.' I said, 'I don't think we're going to have to anyway.' He said, 'promise me,'" Biden told CNN.

The offer clearly touched Biden, whose family was suffering financially and emotionally from Beau's brain cancer recurrence.

Beau Biden, attorney general of Delaware, first experienced complications in the summer of 2010. At the time it was reported he had suffered a mild stroke, though tests showed no lingering issues. During Beau's second term in office, he was diagnosed with brain cancer. He passed away in May 2015.

Obama provided the eulogy at Beau's funeral. The vice president said he would never forget the gesture.

"Thanksgiving was hard," said Biden during the interview with CNN. "The idea of an empty chair, you know, was something no one looked forward to. But everybody -- you know, they're tough. And you know, we're focusing on the inspiration of Beau, rather than loss of Beau."

White House Press Secretary Josh Earnest said the story proves the strength of Obama and Biden's friendship, independent of politics.

"Obviously, the President and the vice president have developed the kind of personal relationship that just transcends their professional responsibilities," Earnest said on CNN's "New Day" Tuesday.