What is XXX's spouse's name?
Sarah Fairbrother
Sarah Fairbrother (calling herself Louisa and known from 1859 as Mrs FitzGeorge; 31 October 1816 -- 12 January 1890) was an English actress and the mistress of Prince George, Duke of Cambridge, a male-line grandson of George III. As the couple married in contravention of the Royal Marriages Act 1772, their marriage was not recognized under the law.
Prince George, Duke of Cambridge