Park's dad, Jamie Sheridan, is, on the surface, a stereotypical "man's man." He's a huge, strong, handsome Army veteran who Eleanor thinks looks "just like Tom Selleck" (21.115-116). He's from an Irish family and lives next door to his parents, and we'll assume that's the house he grew up in—he says he grew up in the neighborhood, and his family's owned their land forever.
Jamie went against the grain in one crucial way, though: When he was deployed to Korea, he met Park's mom, Mindy, fell in love, and brought her home to Omaha. Jamie and Mindy's relationship is one of the sweetest adult relationships we've seen in a book, and years after having kids, they're still hopelessly in love. They're visibly affectionate (which Park complains about), they communicate with each other, and they make thoughtful decisions about their kids. Theirs is the "happily ever after" everyone dreams about.
Still, they're not perfect, and Jamie struggles with accepting Park's differences. He gets incredibly frustrated at Park's inability to learn stick shift, and years of exposing Park to sports and hunting doesn't seem to have made much difference. When Park decides to wear eyeliner, Jamie flips out:
Park wondered if it was just the eyeliner that had done it—or if the eyeliner had been the pencil that broke the camel's back. Like Park had spent sixteen years acting weak and weird and girlie, and his dad had borne it on his massive shoulders. And then one day, Park put on makeup, and that was it, his dad just shrugged him off. (38.56)
But what makes Jamie really amazing is his ability to think through a situation and try his best to understand the people he loves. He's genuinely kind to Eleanor, and when things reach a crisis point with Richie, Park finds out that he can truly depend on his dad for support.