For family tree see John Fullarton on Ancestry (subscription required)
John [1768-1844] and Gavin Fullarton [1788-1876] were sons of Rev John Fullarton, minister of Dalry, Ayrshire [Fasti Ecclesiæ Scoticanæ].
John Fullarton cohabited in Guyana with Charlotte Thomas, one of the daughter of Dorothy 'Doll' Thomas, with whom he had four children. Charlotte's sister, Eliza, was the cohabitee of Gilbert Robertson, from Kiltearn. In 1826 John abandoned his family in Guyana and returned to Scotland, where he married. [Kit Candlin, The Last Caribbean Frontier (Macmillan, 2012).]
Gavin Fullarton entered into a partnership with Allan McDonald, establishing a merchant house in London in 1824. Harry Robertson Watson was taken into the business in Demerara, which then traded as McDonald, Watson & Co. Fullarton and McDonald owned a plantation in Berbice, which was already managed by Watson. [NLS MS 19334 f24 Harry Robertson Watson to his mother (Mrs Traill, Liverpool) from Berbice 18 Nov 1824]
The partnership of Gavin Fullarton and Allan McDonald in Demerara was dissolved in 1837 [London Gazette 19525 25/7/1837].
Gavin Fullarton appointed James Barclay (1838 - 10 Jan 1872) from Saltcoats as manager of plantation Everton, where he died in 1872 having been manager for about 20 years (Ardrossan and Saltcoats Herald - Saturday 17 February 1872).