saying, these are two extraordinary opponents representing two different generations. Biden, 69, ryan, 42. For the first time in history, though, both men are catholic. And they bring two very come... See More
saying, these are two extraordinary opponents representing two different generations. Biden, 69, ryan, 42. For the first time in history, though, both men are catholic. And they bring two very come peopling stories to the stage. Abc's david muir telling us about that. David? Reporter: Great to see you, diane, from kentucky tonight. Let me show you how they're framing the debate. This poster is up all over the place. Thrill in the ville. These two men will be sparring over very different policies tonight,s be as we discovers today, they actually have quite a bit in common. Their political paths both began when they were young. Joe biden, 29 when elected to the senate. Paul ryan, 28 when he went to congress. Both catholic, both celebrate their roots of blue collar america. Joe biden grew up in a tight-knit family, played college football and when his grades suffered, his father stepped in. You've got to be a college man, joey. And I asked, why is this so important? You never went to college. And he said, they can never take that from you. Reporter: Days before he was to be sworn in as that young senator, his wife and 18-month-old daughter were killed in a car accident. Two young boys, badly injured, survived. He was sworn in at his son's bedside. We can always get another senator, but they can't get another four. Reporter: Four years ago, biden spoke of the tragedy. The notion that somehow, because I'm a man, I don't know what it's like to raise two kids alone, I know what it's like to have a child you're not sure is going to make it. I understand. I understand. Reporter: Paul ryan, a family man, too. Three children with his wife. He proposed to his wife while fly fishing in wisconsin. He still lives a block from the house he grew up in. My veins run with cheese, bratwurst and a little spot of miller. Reporter: Back in high school, classmates voting him prom king. They also voted him biggest brown noser. It was what he faced away from school that shaped the young man. At 16, he found his father dead of a heart attack. Ryan himself, now, a fitness buff, working out, leading p-90s classes, and these pictures posted by "time" magazine. Rising republican star, he's known for his controversial budget. How do you feel about being made the boogeyman about this budget business? You know, I don't really think about it. I sleep well at night. Reporter: He probably will sleep well once he gets through this debate, as well. I wanted to show you the audience here, the rounds behind the stage. We do know that paul ryan's wife will be here, his mother will be here, as well. Dr. Jill biden, the wife of the vice president, expected to be here with his three children, as well here tonight. And one member, of course, of our family we keep talking about, martha raddatz, we all had lunch with her today, she said she's ready for the task. All right. David, great to see you there in the hall tonight.
This transcript has been automatically generated and may not be 100% accurate.