Simple, really - the Franz Ferdinand that we're referring to was "Archduke Franz Ferdinand of Austria". Basic summary of the man:
"Franz Ferdinand, Archduke of Austria-Este (December 18, 1863 – June 28, 1914) was an Archduke of Austria, Prince Imperial of Austria, Prince Royal of Hungary and Bohemia, and from 1896 until his death, heir presumptive to the Austro-Hungarian throne. His assassination in Sarajevo precipitated the Austrian declaration of war which triggered World War I."
Hope that helps.