In the early hours of Oct. 7, my cousins from the Kalderon-Dan family on Kibbutz Nir Oz, near Israel’s border with Gaza, woke to the sound of blaring sirens warning of incoming rockets. They immediately headed into their bomb shelters. We did not know this this was a crisis unfolding into an unimaginable nightmare. Now, five members of my family are missing: Carmela, Noya, Erez, Sahar and Ofer, all likely taken as hostages by Hamas into Gaza. We know this from a video we received showing 11-year-old Erez Kalderon being dragged away by violent infiltrators. Carmela Dan is Erez’s grandmother...