Head of the Family (1996)

Lance, the owner of a local diner, is having an affair with Loretta, the wife of a local thug. Lance discovers that a local family, the Stackpools, are a family of mutants, each with a special physical attribute. The family is controlled by Myron, so intelligent he is little more than a head. Lance uses their secret to blackmail the Stackpools with unforeseen consequences.