Among his siblings was older brother William, who served as the Chancellor of the Exchequer and became the 2nd Viscount Barrington upon their father's death in 1734.

In 1756, he was promoted to the rank of Colonel, and appointed aide-de-camp to King George II.

[1] In 1758, the King gave him the colonelcy of the 64th Regiment of Foot, then formed from the second battalion of the 11th, promoted him to the local rank of major-general in the West Indies, and sent him second-in-command of an expedition against the French West India Islands.

In March he used this as a base from which naval transport carried separate forces under Brigadiers Byam Crump and John Clavering to attack French positions around the island.

[2] In June 1759, Barrington was removed to the 40th Regiment, and on 24 October the same year to the 8th, or the King's; he was also appointed Governor of Berwick.