His father married four times and had a total of eleven children, of whom only Sidney and two others survived childhood; his older half-brother Francis (1642-after 1679) and a half-sister Rebecca (1676-after 1699).

[1] A member of one of the wealthiest families in Cornwall, John Godolphin supported Parliament in the Wars of the Three Kingdoms, unlike his Royalist cousins Sidney, killed in 1643, and Francis.

[3] Godolphin attended legal school at the Inner Temple in 1668 but little is known of his activities until June 1685, when he was commissioned captain in the Earl of Bath's regiment, raised by James II following the Monmouth Rebellion.

[2] In August 1688, his regiment was sent to garrison Plymouth, a key strategic port in the West Country; the Earl of Bath, who was governor of the town, defected to William of Orange after his landing at Torbay during the November 1688 Glorious Revolution.

He replaced his cousin the Earl of Godolphin as Governor of Scilly in April 1700 and was commissioned as a major in the Queen's regiment, part of the military expansion caused by the imminent outbreak of the War of the Spanish Succession.