Thanks for your comments, Graham.
I am pretty sure the IGI record was submitted by a researcher and I have not sighted a baptism register entry. Robert's parents were married at Forres in 1791 and children born/baptised successsively at Dyke, Houston & Killellan (Renfrew), Rafford, Rafford, Rafford and Rafford. The 1841 census shows Robert, aged 30 and wife Johanna, aged 25. The 1851 census shows Robert, aged 42, born, M???, Aldearn. His father (also Robert) aged 83 is now living with the family and I have not seen any evidence that he was living in Nigg before then.
Hope these details are of use.
Many thanks again,
Jonathan