Holmes was the fourth son of Colonel Henry Holmes, governor of the Isle of Wight, and his maternal grandfather had been Admiral Sir Robert Holmes, one of England's most noted naval leaders during the Anglo-Dutch Wars of the previous century who had overseen Holmes' Bonfire. Joining the navy at the age of 16, he was promoted to lieutenant in 1734 and received his first command in 1741. For the remainder of the war, he served mostly in the West Indies.