Long’s father, Edward, was the second son of a wealthy clothier from Whaddon, the senior branch of an extensive family. He had an interest in trade and made substantial investments in ships operating from Plymouth and Weymouth.
Other than these details, little has been ascertained of Long’s early life, although he presumably lived in Broughton Gifford before going up to Oxford in 1593. By 1598 he had married the daughter of a wealthy clothier from Bradford-on-Avon, but she died, possibly in childbirth, three years later.
Long’s maternal grandfather and great-uncle, Henry and William Brouncker, had both represented Westbury in the Elizabeth’s reign; this and his own property in the area explains his return for Westbury in 1625. Though unmentioned in the records of his only Parliament, his views may have been influenced by his cousin, Walter Long II*, a critic of the duke of Buckingham.
Long made his will on 30 Mar. 1630, leaving £5 to the poor of Steeple Ashton, where he asked to be buried. He left his younger son Robert £100 upon completion of his apprenticeship to a London merchant, while his daughter Eleanor received £1,500 as a marriage portion; she later married the grandson of Sir James Ley*. His cousin Walter Long II was left a commemorative gold ring. His wife, who was named as his executrix, was given all the household chattels together with the profits of property leased in Bradford and a life interest in Rowde Ashton. The will was proved on 18 Apr. 1635.