Katherine Kate Elizabeth Roberts is a fictional character on the NBC soap opera Days of Our Lives.The matriarch of the series' Roberts family, the role is played by and most associated with actress Lauren Koslow, who has held the role since 1996.ate is the mother of Austin Reed, Billie Reed, Lucas Horton, Philip Kiriakis, and twins Cassie and Rex Brady. Kate is the ex-wife of Curtis Reed, Victor Kiriakis, Roman Brady, and Stefano DiMera.