Watch Rainman Twins for Free: How to Stream the Movie Online at 123Movies. . This is the fascinating story of the only identical twin autistic savant sisters known to exist. Over 50 years time, Flo and Kay have literally memorized the world around them. They never forget a date or a song, what they ate or the weather on any given day. Like the Dustin Hoffman character in the movie Rainman, their lives are riveting. You'll never forget them. They'll never forget you.