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
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,