kel_faz22, you need to take a look at that marriage certificate. SP is Scotland's People. Go to
www.scotlandspeople.gov.uk and invest in 30 credits at a cost of £7.
Use 1 credit to find the marriage in the indexes, and 5 to view and download the certificate. This will tell you the full names of the couple's parents, including their mothers' maiden surnames. It should also tell you if the parents were deceased.
If they were not deceased, use another credit to find the death of George's mother and five to download the death certificate. She should be indexed under both her maiden and her married surnames. This will tell you the full names of her parents, including her mother's maiden surname, and whether she was married or widowed.
This will enable you to narrow down your search for John's death certificate, which will add the names of his parents.
Edit: I see that my post crossed with Isobelw's and that she has already used some of her own credits to look up the marriage for you, and that both John and Ann were deceased by 1856. There is a small chance that one or both died in 1855 or 1856, in which case there would be (a) death certificate(s), but if they died before that there won't be any.