Frederick the Simple, third Frederick to rule Sicily (Trinacria) didn't use regnal number
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Frederick III of Sicily, self-styled the third despite being the second Frederick to rule Sicily (Trinacria)
Sicily | Frederick the Great | Frederick | Frederick II | Frederick II, Holy Roman Emperor | Frederick Russell Burnham | Frederick Roberts, 1st Earl Roberts | Frederick Law Olmsted | Syracuse, Sicily | Frederick I, Holy Roman Emperor | Frederick Forsyth | Frederick Douglass | Frederick, Maryland | Prince Frederick, Duke of York and Albany | Frederick III | Frederick I | Frederick Delius | Frederick William III of Prussia | Kingdom of Sicily | John Frederick II, Duke of Saxony | Frederick III, German Emperor | Frederick William IV of Prussia | Frederick Schomberg, 1st Duke of Schomberg | Frederick I, Margrave of Brandenburg-Ansbach | Frederick III, Holy Roman Emperor | Frederick, Prince of Wales | Frederick Funston | Frederick Ashton | Allied invasion of Sicily | John Frederick II |