Sir Augustus Frederick d'Este, KCH was a relative of the British royal family and the earliest recorded person for whom a definite diagnosis of multiple sclerosis can be made. He was the only son of Prince Augustus Frederick, Duke of Sussex and his wife Lady Augusta Murray. He was a grandson of George III, nephew of George IV and William IV, and a first cousin to Victoria, Queen of the United Kingdom.

Prince Augustus Frederick, Duke of Sussex, was the sixth son and ninth child of King George III and his queen consort, Charlotte of Mecklenburg-Strelitz. He was the only surviving son of George III who did not pursue an army or navy career. A Whig, he was known for his liberal views, which included reform of Parliament, abolition of the slave trade, Catholic Emancipation, and the removal of existing civil restrictions on Jews and Dissenters.