Complex sentence: There is a legend that William Pitt the Younger thought of her; the somewhat notorious lover of Julie de Lespinasse, Guibert, a cold-hearted coxcomb of some talent, certainly paid her addresses.
Split into simpler sentences: There is a legend that William Pitt the Younger thought of her. The somewhat notorious lover of Julie de Lespinasse, Guibert, a cold-hearted coxcomb of some talent, certainly paid her addresses.