If I describe a famous classic work of fiction as follows:
A young orphaned chivalrous knight fighting a powerful lord meets a wise old man who will serve as his mentor, and saves a young lady who was also adopted; he starts falling in love with her, but they eventually discover that they are, in fact, brother and sister, and also that they are the powerful lord's next-of-kin, and the lord in question turns out to be not so evil after all.
What is the first work that comes to mind?
The answer, of course, is that I am summarizing the 1779 play Nathan der Weise (“Nathan the Wise”) by G. E. Lessing, one of the most renowned plays of the German enlightenment, taking place in Jerusalem during the Third Crusade: the lord is Saladin, the wise old man is the titular character Nathan, and the knight and the lady he saves (and who turns out to be his sister) are a young Knight Templar and Nathan's adoptive daughter Recha.
But I'm sure that even without the context, many people would think of Star Wars before they thought of Nathan the Wise.
Now admittedly you may say I cherry-picked my summary to make it seem as similar to Star Wars as possible (for example, in Nathan the Wise, the brother and sister turn out to be the powerful lord's nephew and niece, not children; and there are, of course, many characters or elements with no correspondence). Nevertheless, the “young knight saves young woman, starts falling in love with her, and later discovers that she is her sister” plot twist seems a bit too specific to be purely coincidental.
What I find immensely surprising is that nobody seems to mention, let alone discuss, this similarity between two very famous stories. (If you google both titles, for example, nothing of interest comes up.) Is it just because sci-fi fans don't read much German 18th-century theater and vice versa? Maybe.
So anyway, question: is there any evidence for or against the possibility that George Lucas was acquainted with, had read, or was influenced by Lessing's play? Or, on the contrary, that it might just be a coincidence? Has anyone ever asked him about it?