John "Jack" Arnold (Dan Lauria) is Kevin's father; a gruff, laconic man and a Korean War veteran; he grew up during the Great Depression, served in the US Marine Corps right after he graduated from college, and is seen in photographs wearing the uniform of a First Lieutenant.
Norma Arnold (née Gustafson) (Alley Mills) is Kevin's homemaker mother who was born on March 22, 1930.
She eventually gets her degree late in the series and begins work at a software startup called Micro Electronics.
When Karen moves in with her boyfriend Michael (David Schwimmer) during her freshman year of college, she has a falling-out with her father.
Karen ultimately accepts some of her parents' viewpoints and has a baby, while her husband learns to support his wife and child.
In the final season, he begins a serious relationship with a divorcee named Bonnie but is left heartbroken when she reconciles with her ex-husband.
Paul Joshua Pfeiffer (Josh Saviano): is Kevin's long time best friend, a bright and excellent student and allergy sufferer.
In the epilogue of the final episode, it is revealed that Winnie travels overseas to study art history in Paris.