Hi Kerry
Did his parent's names come from the informant on his death record?
The IGI has a record for a Mary MARSHALL born & chr in Markinch 1798 with parents John MARSHAL & Margaret ROBISON. It's on Batch C114475 (Markinch births, extracted)
On the same batch, are a number of records of issue to a John MARSHAL & Marg(a)ret ROBERTSON:
James 1800
William 1802
Margaret 1804
John 1805
Ann 1809
Alexander 1811
Isobel 1812
I think Mary b 1798 may be part of the same family. I have seen ROBISON and ROBERTSON in early record as interchangeable, before.
There is also a marriage on the IGI:
John MARSHALL & Margaret ROBERTSON, 5 Nov 1797, Falkland Fife.
Cheers
AMBLY