Charles Seymour, 6th Duke of Somerset the pride of birth and rank amounted almost to a disease". Charles was the second son of Charles Seymour, 2nd Baron Seymour of Trowbridge (died 1665), of Marlborough Castle in Wiltshire, by his wife Elizabeth Alington (1635–1692). The 2nd baron was (in a junior line) a great-great-grandson of Edward Seymour, 1st Duke of Somerset (executed 1552), brother of Queen Jane Seymour, uncle of King Edward VI and Lord Protector of England. Charles was educated at Harrow School and Trinity College, Cambridge, where his portrait by Nathaniel Dance-Holland survives in the College's collection. In 1675, Charles's elder brother Francis Seymour, 5th
Duke of Somerset On his death without issue on 29 April 1675 only the Marquessate of Hertford became extinct. His distant cousin Francis Seymour, 3rd Baron Seymour of Trowbridge (1658–1678) became 5th Duke of Somerset. Francis was the eldest surviving son of Charles Seymour (1621–1665), whose father Sir Francis Seymour (c. 1590–1664), a younger brother of the 2nd Duke of Somerset, had been created Baron Seymour of Trowbridge in 1641. When the 5th Duke died unmarried in 1678, the title passed to his brother, Charles Seymour (1662–1748), youngest son of the 2nd Baron Trowbridge. The 6th Duke, was known as "the Proud Duke",