Johnston was
christened at
Stromness, February 25, 1724. He was the second son of John Johnston (1690−1757), 3rd
Laird of Outbrecks on the
Orkney Mainland, and his wife Marjorie Crafts (1695−1774), daughter of John Crafts who had been an
ensign in
Cromwell's army before becoming a
ship-owner at
London. The Johnstons/
Johnstones of Outbrecks (sometimes spelt Outhrecks) were a prominent Orkney family and James' father - one of the principal merchants there - had added to their land by acquiring considerable property throughout the
islands at Harray,
Stenness and
South Ronaldsay etc., owning one-third of the town of Stromness itself. Johnston's elder brother, Joshua Johnston (1720-1794), married an
heiress of the Halcro family and lived at Orphir House, becoming the first Laird of Coubister; they were the ancestors of
Henry Halcro Johnston. James and Joshua's sister, Elizabeth, was the mother of
James Irvine, of
Quebec City. James Johnston was a cousin of Joseph Isbister (1710−1771), who in 1740 became the first
Orkneyman to receive a governorship in the
Hudson's Bay Company and settled in
Quebec in 1760. Another of James's sisters, Katherine Johnston, had married George Geddes (1717−1791), great-grandson of Bishop
George Graham. Geddes' father, David Geddes, aside from being Collector of
Customs and owning a merchants bank and shipping business, also owned the first agency that supplied
Orkney men for work in the
Hudson's Bay Company, consisting of three quarters of their workforce in
Canada. Through these connections, Johnston and his brother-in-law were in
Quebec with General
James Wolfe at the
British Conquest of New France in 1759. He probably returned home soon afterwards, but by 1761, Johnston was renting a house in
Quebec City and in July, the following year, he established a business partnership with
John Purss who was to remain his partner and closest friend up until his death. ==Public Life at Quebec==