Complex sentence: As Headmaster of Harrow School, he married 15 December 1831 Caroline Sophia Parnell, whose brother George Damer Parnell was the curate of Ash, 1859--1861.
Split into simpler sentences: As Headmaster of Harrow School, he married Caroline Sophia Parnell on 15 December 1831. Her brother George Damer Parnell was the curate of Ash, 1859--1861.