Fox was bred by Sir Ralph Assheton (1651-1716), 2nd Baronet of Middleton, who had acquired two mares from Englebert Leedes, both of whom were covered by Clumsey, one of which produced Fox and the other Fox Cub (b c 1714). Sir Ralph's estate, Whalley Abbey, in Lancashire, is thought to be the source of the breed of cattle called British Whites. Fox was later acquired by Matthew Lister, John Manners (1676-1721), the 2nd Duke of Rutland, Mr Cotton and eventually the Earl of Portmore.

His description in the Sportsman's Pocket Companion reads:

The Portraiture of Fox,
The Property of his Grace the Duke of Rutland

Fox was in high Esteem for Running & likelwise [sic] for a Stallion he was bred by Sir Ralph Assheton Bart, but was afterwards the Property of Esqr Lister of Yorkshire he was got by Sir George Warburton's Clumsey who was bred by Mr Wiks [sic] & got by Old Hautboy bred by the Darcy Family out of a Royal Mare got by the Darcy White Turk. Fox's Dam was Bay Peg his Grand Dam Young Bald Peg both bred by Mr Leeds & got by his Arabian Sire of Leedes, his Great Grand Dam was the Dam of Spanker Son of the Darcy Yellow Turk his Great Great Grand Dam was the Old Moorocco [sic] Mare call'd Old Bald Peg She was bred by General Fairfax out of a Foreign Mare & his Moorocco Barb.

Fox 1719 when 5 Years Old won the Ladies Plate at York then the Property of Esqr Lister who disposed of him to his Grace the Duke of Rutland in whose Possession he beat the Duke of Wharton's Stripling at Newmarket for a Considerable sum; he won 2 King's Plates at Newmarket & 1 at Lewes & receiv'd 250 Guineas forfeit of the Duke of Wharton's Swallow; he then became the Property of Esqr Cotten [Cotton] of Sussex in whose hands he won a Prize of 300 Guineas at Quainton Meadow, he beat Lord Hilsboroughs Witty G a Match for near 20000 Pounds he receiv'd 100 Guineas forfeit of Lord Hilsboroughs Witty G, he beat Lord Drogheda's Snip & 3 Matchbox [Matches] for Considerable Sums, and Mr Frampton's Miss Worsop 200 Guineas: he was Sire of several Excellent Horses, he made his Exit 1738 in his 23 Year, then the Property of the Earl of Portmore.

Fox raced mostly at Newmarket, from 1719 to 1723, for a number of owners. In Lord Portmore's stud he produced a number of good sons, including  Cub (ch c 1739), sire of the famous Cub Mare*, an early American matriarch and ancestress of Nearco (br c 1935), Merry Andrew (b c 1739) and Bolton Goliah (b c 1730). He also sired the three useful brothers, Quiet Cuddy (ch c 1727), the Devonshire Conqueror (gr c 1725) and the Appleyard Conqueror (ch g 1728). Dabster* (ch c 1736) appears in early traditional Virginia pedigrees.

His daughters proved of equal worth. Meliora (ch f 1729) produced Tartar (b c 1743 Croft's Partner), the sire of King Herod (b c 1758), a Champion Sire and progenitor of the King Herod sire line. Sister to Slipby (br f 1738) produced the Champion Sire Snap (bl c 1750 Snip) and was ancestress of the St Leger winner and excellent sire Hambletonian (b c 1792 King Fergus). Fox Mare produced Janus* (ch c 1846) who left an indelible mark on American bloodstock. Other unnamed Fox Mares were foundation stock in Family 29, Family 31 and Family 33, as was The Cat Mare in Family 55.

A half brother to Basto¹ (br c 1703 Byerley Turk), Fox was Champion Sire in 1731 and 1735. He died in the spring of 1738.

¹ Basto and Fox are not said to be from the same mare, Bay Peg, until the 5th Edition of Volume 1 of the General Stud Book published in 1891. There is no indication, either in advertisements or on their portraits, that Basto and Fox were half-brothers, although it seems likely that they both eventually trace to Old Bald Peg.