On 11 September 1744, with the unexpected death of George Seymour, Viscount Beauchamp (1725–1744), the only son of Algernon Seymour, 7th Duke of Somerset, the likelihood emerged of Seymour's father succeeding a distant cousin as Duke of Somerset, as the Duke was then aged sixty and his wife was past child-bearing age. On 23 November 1750 the Duke died, Seymour's father duly succeeded to his titles, but not most of his estates, and Seymour thus gained the courtesy title of Lord Francis.[4] Being the son of a Duke gave him better prospects of advancement.
When his elder brother Webb Seymour's male line died out in 1923, Lord Francis Seymour's great-great-grandson Colonel Edward Seymour inherited the family estates and became 16th Duke of Somerset, although it took him until 1925 to establish his claim to the dukedom.[4]