I found two entries in the IGI for their marriage , one in Elgin and the other in New Spynie...I'm presuming that you know this. Do you have any more info on the couple which might help such as dates of births? Every little snippet helps
I had a quick look in the Free Census site http://freecen.rootsweb.com/cgi/search.pl at the 1841 Census and there are a few possibilities if they stayed in the Moray area.
You might be best to look for their death certificates on Scotland's People http://www.scotlandspeople.gov.uk/ If they died after 1855 then you'll find them there and the certificates will give you their parents names. I'd start looking for Janet's first as you have her Maiden name and that makes the searching easier. A search produced 2 results for a Janet Sinclair/Watson in Moray between 1855 and 1910...