Seymour was the second son of Henry Seymour, of Langley, Buckinghamshire Groom of the Bedchamber, and his second wife Ursula Austen, daughter of Sir Robert Austen, 1st Baronet,[1] and widow of George Stawale.
He was the paternal grandson of Sir Edward Seymour, 2nd Baronet, and wife Dorothy Killegrew.
[4] Seymour was returned unopposed as Tory Member of Parliament for East Looe at a by-election on 17 January 1699 in the interest of his cousin Bishop Trelawny of Exeter.
Returned again at the 1708 British general election, he voted against the impeachment of Dr Sacheverell in 1710.
He was one of the 'worthy patriots' who detected the mismanagements of the previous administration and a member of the October Club.