Karen Arnold

Karen Arnold is Kevin's older sister, a teenager drifting into the counterculture of the late sixties—beads, protest posters, a boyfriend her father distrusts. She rolls her eyes at suburban convention, clashes with Jack over curfews and values, and treats Kevin with the offhand mix of scorn and tenderness particular to older siblings.

She gives the show its generational friction without turning into a lecture: her rebellion is played as real teenage conviction, not a punchline, and Olivia d'Abo lets flashes of vulnerability show through the defiance. Karen makes the era's upheaval domestic, arguing about it at the dinner table instead of on a picket line.