Sebastian's words cut, visibly, as fat tears gather and finally track their way down Ciel's temple, uplifted as his face is by Sebastian's hand. He can easily imagine what Sebastian's done to his parents, what he's done to everyone Ciel cares about. He bites back the whimpered "Father, Mother," that wants to escape, pushes back the urge to call out for someone to help him, please, because he's so incredibly overwhelmed and outclassed that he doesn't know how to fight back against Sebastian's physical and mental assault.
He glares up at Sebastian, the beginnings of hatred and darkness starting to build, and bites out through his clenched teeth:] Until they've suffered the same pain I have.