Complex sentence: In 1671 her nephew Louis Joseph, Duke of Guise died; she and the young widow fought over who would be guardian of the late Duke's little son, François Joseph, the last male of the House of Guise.
Split into simpler sentences: In 1671 her nephew Louis Joseph, Duke of Guise died. She and the young widow fought over who would be guardian of the late Duke's little son, François Joseph, the last male of the House of Guise.