How did Chris McCandless and Jon Krakauer's fathers age differently?

I think their fathers had more similarities than differences. Both fathers wanted something different for their sons. Jon's father, like Chris's, was opinionated, well-educated and headstrong. Jon's father expected perfection and, for a time, Jon tried to deliver. Much like Chris, Jon became alienated with his father and his beliefs. He thought his father was part of the artificial consumer mentality and did not seek what was "real" in life. Like Chris's father, Jon discovers that his father had lived a double life. Chris's father had a different family altogether. I'm not clear on what exactly Jon's father did but Jon felt him to be a hypocrite in the highest order. Jon's father eventually develops post-polio syndrome. He self-medicates and loses his sanity. Both Chris and Jon share such similar father issues that Krakauer has been criticised for being overly sympathetic to Chris in his book.