Complex sentence: René Hérault was also the grandfather of the famous Duchess of Polignac, friend and confident of the queen Marie Antoinette, who was the daughter of Jeanne Charlotte Hérault (1726-1756), herself the daughter of René Hérault and his first wife.
Split into simpler sentences: René Hérault was also the grandfather of the famous Duchess of Polignac, friend and confident of the queen Marie Antoinette. The Duchess of Polignac was the daughter of Jeanne Charlotte Hérault (1726-1756), herself the daughter of René Hérault and his first wife.