Rob Reiner and Cary Elwes. Charley Gallay/Getty Cary Elwes starred in Rob Reiner's 1987 movie "The Princess Bride." Elwes last worked with the director on Reiner's 2016 movie "Being Charlie." Reiner's son, Nick, wrote the screenplay about his struggles with drugs and mental health. Cary Elwes will always be indebted to Rob Reiner for giving him his big break in show business, casting the then-unknown British actor in the lead role of his beloved 1987 movie "The Princess Bride." So when Reiner called Elwes 29 years later to ask him to be part of the most personal project of the filmmaker's career, the actor was more than willing to oblige. "He told me that I would be playing a character who is very similar to him because he wanted to explore the family dynamic of having a child who was having mental issues," Elwes told Business Insider of his role in the 2016 indie film "Being Charlie." Elwes said he "jumped at the opportunity" to work with Reiner again.…