In the late ’60s, the McKerrow family of Helena, Montana, had three sons: one adopted, two biological. Today it has a daughter, transsexual middle sibling Kim, who returns from New York to film her 20-year high-school reunion. Confounding every red-state cliché, her old pals seem remarkably friendly and open-minded. Instead, it’s her older, adopted brother who has problems. Director Kimberly Reed, who also changed her surname, thrusts us uncomfortably close into a complicated family dynamic: She’s asking others to accept “my transition” (most do), while also seeking to reconcile with Marc, a Spokane resident now harboring many resentments, popping various meds, and suffering residual brain damage from a long-ago car crash (never explained). Then Reed adds a still-more-complicated family dynamic: Marc was adopted (in Tacoma) from the daughter of Orson Welles and Rita Hayworth; and though he can play piano by ear and shares the bulk and brow of his famous grandfather, there’s precious little stardust in his life. When Reed follows him to Croatia to meet Welles’ last girlfriend, the reunion is no happier than the holidays back in Helena. She seems to think, as so many in the reality-TV era do, that simply running the camera will be therapeutic; that, as Marc grows increasingly volatile, videotape can be a substitute for Haldol. But brain injuries, like families, can’t always be mended. Split between two subjects, Prodigal Sons gradually collapses into non-conclusion. Whatever assurance Reed has found as a woman, she lacks as a filmmaker.