Edward Douglas John Hay was born on 6 August 1947 as the elder of twin sons. He became an insurance broker before succeeding his father in the marquessate. Tweeddale was descended from George Hay, 8th Marquess of Tweeddale, the common ancestor of all subsequent holders of the title.
He was educated at Milton Abbey and Trinity College, Oxford (Bachelor Honours).
Along with the marquessate and its subsidiary titles he succeeded as Hereditary Chamberlain of Dunfermline. Lord Tweeddale died on 1 February 2005, aged 57, and was succeeded by his younger twin brother David Hay. The Hays of Yester were possibly related to the Hay earls of Erroll, who held prominent ceremonial office under the Scottish Crown.
Sonia Peake, daughter of Osbert Peake, 1st Viscount Ingleby.
The next heir is their youngest fraternal brother Lord Alastair Hay, styled Master of Tweeddale as heir presumptive. Since none of the three brothers (sons of the 12th Marquess"s first marriage) are married, the next in succession are their two half-brothers, sons of the 12th Marquess"s second marriage.
The two half-brothers are also twins, but the eldest of the two, Lord Andrew Arthur George Hay, is the only one with issue. The 13th Marquess is remembered chiefly for being one of the few British peers to be succeeded by a younger twin brother.
Similarly, the 3rd Earl of Durham (1855–1928) was succeeded in 1928 by his younger twin brother, the 4th Earl (1855–1929).
The 3rd Viscount Knutsford (1855–1935) also succeeded an older twin, the 2nd Viscount (1855–1931 dspm) on 27 July 1931.
