The link between Robertson and Sweet began when Catherine Robertson (1770 to 1832) in 1787 married Thomas Sweet (1758 to 1848). Catherine was the daughter of John Robertson (John of the Bank). John and his brothers, William and James, were well known (well-recorded) merchants in Glasgow and their history is very interesting.
A further twist to the tale is that two sons of Catherine and Thomas travelled to Jamaica to work on their uncle’s plantation; one died and one moved on to America. I have found neither.
There are several Robertson septs, this one is Robertson of Kindeace. It is this branch of Robertson that provides a mother for William Ewart Gladstone. Anne MacKenzie Robertson married John Gladstone in 1800 and among their six children William Ewart Gladstone was the fifth born in 1809.