|Source: Syd Chaplin: A Biography by Lisa K. Stein|
Sydney Chaplin is standing at far right. Sydney, who had been absent from Hollywood since 1927, came to work for Charlie on the set of The Great Dictator. Although he was never given a title or had any real authority, it was Sydney who suggested Jack Oakie for the role of Benzino Napaloni.
Another note: most of the signs in the ghetto scenes are in the international language Esperanto. Read more about Esperanto & The Great Dictator here.