John Thomas Ruskin (1761-1817), the paternal grandfather of John Ruskin was born in London. His father John Ruskin (1734-1780) had been baptised in Cheshunt in 1735, later living in Marylebone, and moving to the Parish of St. Bartholomew-the-Great where he became Parish Clerk (see Viljoen, Ruskin's Scottish Heritage pp. 40-41). John Thomas was indentured to a vintner at the age of fifteen. He later moved to Edinburgh, established a small grocery business, and married Catherine Tweddale, a Scottish girl from a land owning family. They had two children, Janet Ruskin (1783-1828) (known to Ruskin as Aunt Jessie) and John James Ruskin, who was to become the father of John Ruskin. They first lived in Edinburgh Old Town and were later able to move to a better location at 15, St. James Square in Edinburgh New Town where they were joined by Margaret Cock (or Cox) (see Margaret Ruskin), Ruskin's future mother.
John Thomas Ruskin worked as an 'agent for Scotland' for T. I. Moore of London, probably in the grocery business, but gradually fell into serious financial debt. John James Ruskin described his father as: 'more magnificent in his expenditure than mindful of his family; so indiscriminate and boundless in his hospitalities that, when the invited guests arrived, he would sometimes have to inquire their names' ( Works, 35.lix). John James eventually repaid his fathers debts after many years of labour. In 1809, John Thomas Ruskin, Catherine and Margaret moved to Dysart in Fife and by 1815 were living in Perth at Bowerswell House. At Bowerswell, Catherine died suddenly in 1817, to be followed ten days later by John Thomas Ruskin, probably by 'cutting his throat' (see Viljoen, Ruskin's Scottish Heritage p. 167).