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
Charles Seymour, 6th Duke of Somerset to the dukedom created for and forfeited by his own great-grandfather, Edward Seymour, 1st Duke of Somerset (executed 1552). Three years later, in 1678, Charles's brother, the 5th duke, was murdered in Italy, aged 20, unmarried and without progeny, having been shot at the door of his inn at Lerice. The 16-year-old Charles Seymour became the 6th duke and the 4th Baron Seymour of Trowbridge. In 1682, at the age of 20 he married a great heiress, the 15-year-old Lady Elizabeth Percy (1667–1722), daughter and sole heiress of Joceline Percy, 11th Earl of Northumberland (1644–1670), who brought him immense estates,