What is XXX's spouse's name?
Cecilia Underwood, 1st Duchess of Inverness
Cecilia Underwood, 1st Duchess of Inverness (née Lady Cecilia Letitia Gore; c. 1785 -- 1 August 1873) was the second wife of Prince Augustus Frederick, Duke of Sussex, sixth son of George III. As their marriage was in contravention of the Royal Marriages Act 1772, it was considered legally void, and she could not be styled either as the Duchess of Sussex or a Princess.