William Mellon has rounded out the cast of his coming feature, “Discomfort, Texas, ” a film loosely inspired by the loss of his own twin sister. The cast will feature Jack Shaw, Mallory Higgins, Maya Boyce and Claire Young, with special appearances by Carla Gallo (Apple TV’s “Platonic”) and Lauren Lane (“The Nanny”) as Nancy. ​Shaw will play Frank Hines, “a sensitive, emotionally stunted young man” coping with the impending loss of his twin sister. Higgins will star as Jane Hines, Frank’s “