There are 3 marriages for Robert born about 1791 and they may all pertain to him. Robert Gillespie married 3rd Jean Maxwell 20 Oct 1832
Laurieston Presbyterian, Falkirk, Stirling, Scotland
I could only find the 1851 census transcription on find my past, it would be worth checking Scotlands People for the detail.
1851 Back Row, Falkirk – GILLESPIE, born Falkirk
Robert 60 a Moulder, Jean wife 35
Children; Miller 21 (Labourer), Jean 13, Ketherine 8, John 6 & Agnes 4
A Miller Gillespie died Greenwich, London Q2/1858 - Vol 1D page 410.
As this is quite an unusual name it could well be him. I would imagine he was named after his grandmothers surname.
Hope this helps.
Colin