Billy had been born in 1865 in Girvan in Ayrshire. His father, an Ayrshire-man, who had married in West Calder a girl from Kirkliston, was a slater, the trade William Jnr. would later follow too. And in about 1870 moved the family to Glasgow, in fact back to Glasgow, where events came to it in a sad tsunami. In 1874 Billy's mother died at the age forty-one. Billy was nine. His father then remarried in 1875, moving to Govanhill but his new wife would herself died in 1877, followed just a year later by William Snr. himself. Billy was an orphan at fourteen, who was brought up with his younger siblings by an elder sister before himself taking on the care, moving to The Gorbals. 

Meantime, he had learned his football locally and begun his playing career with Govanhill F.C.. That was before in 1884 at nineteen joining the nearest senior team, Third Lanark, from where at twenty-one he would be capped for the first time, in 1889 in a twice-played victory over Celtic earn a Scottish Cup winners' medal and a second international appearance, followed by a third the next season. And it must have been shortly after that he started a relationship with Grace Hamilton nee Shaw, a widow seven year older than he. She had in 1878 married in Old Monkland, had a son in 1888 with her husband dying in Glasgow in 1890 but crucially been born in Rothesay, which is where in 1895 on hanging up his boots that Billy Johnston moved, working still as a slater but playing for the local Bute Casuals and later training Bute Athletic, and to where she returned. 

Billy and Grace would on Bute have a daughter in 1897, a second in 1899 and a son in 1901 but they would for reasons unknown not marry until 1902, still on the island, before returning post 1909 to the mainland and Glasgow, first to the east of the city and then the west, close to where he spent his childhood years. And it was there in Finnieston that in 1946 at the age of eighty-eight that Grace would pass away, Billy following her four years later in 1950 at eighty-five.