Mary Erskine lived on a close off the High Street in Edinburgh, to the east of St Giles' Cathedral, and close to the Cowgate, then a fashionable suburb. She was born at Garlet House, Clackmannanshire, in 1629. Little is known of her early life, but in 1661 she married Robert Kennedie, a writer (i.e., a lawyer) and they had five children, three boys and two girls, all of whom appear to have died in infancy. Robert Kennedie died in 1671 leaving Mary with considerable debts, although she managed to pay these off through careful management. On 23 September 1675, Mary Erskine married her second husband, James Hair, in North Leith.  James Hair was a chemist, and owned a chemist's shop on the High Street. He was considerably younger than Mary Erskine, but he too died in 1683. By the contract of marriage, Mary Erskine inherited most of what belonged to her husband. It seems that this was not a large sum of money, but she used the money to set up a private bank, and built up a considerable fortune.
She died in 2 June 1707 and was buried two days later in Greyfriars Kirkyard at the end of the section known as the Covenanters' Prison.