Seymour, John, 4th Duke of Somerset -1675)
John Seymour, 4th Duke of Somerset and 5th Marquess of Hertford, was the fourth son of William, the 2nd Duke, and his second wife, Frances Devereux, eldest daughter of Robert Devereux, Earl of Essex. He married Sarah, daughter and heir of Sir Edward Alston, and widow of George Grimston in 1656. He was Member of Parliament for Marlborough 1661 1671, and was Lord Lieutenant of Wiltshire and Somersetshire in 1672. He succeeded his nephew William 26 September 1671. He died childless in 1675, when the Marquessate became extinct and the other honours devolved on his cousin, Francis Seymour, 5th Duke.