Her Sister's Keeper is a Catwoman storyline written by Mindy Newell with illustrations by J.J. Birch. It's published in the 1989 Catwoman mini-series, marking the first time Selina Kyle received her own title. This is Newell's second Catwoman story, following her arc The Tin Roof Club in Action Comics Weekly. The story is a companion piece to Frank Miller's Batman: Year One, expanding on Kyle's actions during that story. This series is one of many Post-Crisis reboots, establishing Catwoman's origin story in the New Earth continuity following Crisis on Infinite Earths.