Task: Question Understanding
Input (English): Context : 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. 
Question : What is Sarah Fairbrother's spouse's name?
Output (English): spouse