Complex sentence: In her early twenties, she had an affair with the married Archduke Franz Salvator, Prince of Tuscany, son-in-law of Emperor Franz Joseph I through his marriage to Archduchess Marie Valerie of Austria.
Split into simpler sentences: In her early twenties, she had an affair with the married Archduke Franz Salvator, Prince of Tuscany. He was the son-in-law of Emperor Franz Joseph I through his marriage to Archduchess Marie Valerie of Austria.