Complex sentence: In 1251, Jeanne married secondly Jean de Brienne, Grand Butler of France, by whom she had a daughter Blanche de Brienne, Baroness Tingry (1252--1302) who married William II de Fiennes, Baron of Tingry.
Split into simpler sentences: In 1251, Jeanne married her second husband, Jean de Brienne, Grand Butler of France. Blanche married William II de Fiennes, Baron of Tingry.