(CNN) - Joe Biden and Meghan McCain shared an emotional moment Wednesday, with the former vice president consoling the daughter of his friend and onetime political rival Sen. John McCain.
Visiting ABC's "The View" to talk about his book, "Promise Me, Dad: A Year of Hope, Hardship, and Purpose," Biden was asked by McCain, a co-host on the morning show, about his son Beau's cancer diagnosis.
McCain's father was diagnosed with glioblastoma, an aggressive brain tumor, in July. Beau Biden passed away from the same cancer in 2015.
"This is the hard part, bear with me, OK? I couldn't get through your book, I tried. Your son Beau had the same cancer that my father was diagnosed with six months ago," McCain said, apologizing as she began to choke up.
"I think about Beau almost every day and I was told -- sorry -- that this doesn't get easier, but that you cultivate the tools to work with this and to live with this. I know you and your family have been through tragedy that I couldn't conceive of -- what would you tell -- it's not about me, it's about everyone with cancer," McCain said, crying as Biden walked over, switching seats with another host to sit next to her.
"Look, one of the things that gave Beau courage, my word, was John (McCain). Your dad, you may remember when you were a little kid. Your dad took care of my Beau," Biden told her, holding her hand.
His son became friends with McCain, Biden said, noting that when he was sick, Beau "talked about your dad's courage, not about illness, but about his courage."
Biden called McCain "one of my best friends." The two served together in the Senate for years before running against each other in the 2008 presidential election.
"We're like two brothers who were somehow raised by different fathers or something because of our points of view," Biden said. "Even when your dad got mad at me, said I should get the hell off the ticket, and remember what I said about your dad? I said, I know, and I mean this sincerely, I know if I picked up the phone tonight and called John McCain and said, ... 'I need your help, come,' he'd get on a plane and come. And I would for him."
Biden cited ongoing research and work on glioblastoma, encouraging McCain to remain hopeful.
"There's breakthroughs that are occurring now, there's four things that are going on, and it can happen tomorrow," he said. "You gotta maintain hope. There's hope. Hope -- you have to have hope," Biden said.
"I swear, guys, we are gonna beat this damn disease, we really are," he added.
John McCain thanked Biden later Wednesday afternoon.
"Thank you @JoeBiden & the entire Biden family for serving as an example & source of strength for my own family," he tweeted.
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