Hectus Julius Caesar and the Brother Sisters

Many people in egypt before then engaged in brother sister marriage. Cleopatra and her siblings did not get along. They had murderous relationships with each other. She was at war with her older brother, and she a, she possibly had poisoned her younger brother and probably ordered the murder of her sister. So it's not a pretty picture. And then the famous story, true or not, i keep wondering what would have happened had shakespeare not not talked about these things.