William Seymour, 2nd Duke of Somerset was the great-grandson of Edward Seymour, 1st Duke of Somerset (c.1500-1552), the uncle of King Edward VI and Lord Protector of England. Seymour made a secret marriage at Greenwich on 22 June 1610 to Arbella Stuart (d.1615), daughter of Charles Stuart, 1st Earl of Lennox and Elizabeth Cavendish. Arbella was thirteen years his senior, and King James I disapproved of the marriage as the union of two potential Tudor pretenders to the throne, who were respectively fourth and sixth in line, could only be seen as a threat to the ruling dynasty. As a result, William was condemned to life
Duke of Somerset Duke's death he was succeeded by his eldest son Edward Seymour (1717–1792). He died unmarried and was succeeded by his brother Webb Seymour (1718–1793) who became the 10th Duke. His son Edward Adolphus Seymour (1775–1855) was a noted mathematician and became the 11th Duke upon his father's death. He changed the family name to St. Maur but Seymour was still very often used. The 11th Duke was succeeded by his eldest son Edward Adolphus Seymour (1804–1885) who was created Earl St. Maur, of Berry Pomeroy in 1863. His eldest son who predeceased him Edward A. F. Seymour (1835–1869) was known