Blood’s thicker than the mud in the family affair that is My Heart Can’t Beat Unless You Tell It To, a contemporary vampire tale utterly stripped of the genre’s romance. In place of mythic hoohah, writer-director Jonathan Cuartas focuses on the grim, quotidian details of day-to-day caregiving for an extremely pale invalid named Thomas (Owen Campbell), a frail wisp of a young man who is wholly dependent on older siblings Dwight (Patrick Fugit) and Jessie (Ingrid Sophie Schram) for survival, sheltered inside a drab house on the forgotten edge of an anonymous city, its every window blanketed from fatal sunlight. […]