Katherine "Kate" Kane is the twin sister of Beth Kane (Alice). She is the cousin of Bruce Wayne (Batman) and Bette Kane (Flamebird / Hawkfire), and the step-niece of Kathy Webb-Kane (the first Batwoman / Headmistress).
Notes:
Kate Kane first appeared in 52 (DC, 2006 series) #7 (August 2006). She first appeared as Batwoman in issue #9 (September 2006).