Complex sentence: On 26 September 1918, Renault (age 40) married Christiane Boullaire age 21 (1897--1979), sister of French painter; subsequently having a son Jean-Louis (24 January 1920-1982).
Split into simpler sentences: On 26 September 1918, Renault (age 40) married Christiane Boullaire age 21 (1897--1979), sister of French painter. They had a son Jean-Louis (24 January 1920-1982).