What is Kevin Arnold's older sister's first name?

Kevin Arnold's older sister's first name is Karen.

Karen Arnold is Kevin's rebellious older sister in the original The Wonder Years, played by Olivia d'Abo. Born around 1952, she is portrayed as a free-spirited young woman whose countercultural views often clash with her conservative father, Jack.

Karen's story develops beyond the Arnold household. During college, she moves in with her boyfriend Michael, causing a serious falling-out with Jack. They later marry and move to Alaska, where Michael finds work on the Alaska Pipeline.

A common mix-up is confusing Karen with Wayne Arnold, Kevin's older brother, or Winnie Cooper, Kevin's friend and romantic interest. Karen is the older sister; Winnie is the neighbor whose first name is actually Gwendolyn.