Yes, that is our family but I am descended from William's brother John Forbes who emigrated to Canada in 1832. Both William and John's parents were George Forbes and Margaret Ross. I have a Scottish cousin who is descended from William and Marion and yes, that is the date of their marriage.
We could not find any birth record for William's father George Forbes. There is a birth record for a George Forbes to a James Forbes of Evelicks. We feel that this is likely not his father as our George Forbes was linked more closely to Pronsy Farm. It is more likely that George's parents were a William Forbes of Pronsy and Margaret Murray of Dalnamain. William Forbes of Pronsy and Margaret Murray married December 26, 1739. Our George Forbes was likely born circa 1755 but knowing how many children these families tended to have, they still are good candidates for being his parents. (We only found one birth entry for William Forbes of Pronsy and Margaret Murray - a son James born 1758). This James would therefore be our George's brother (our George being born circa 1755).
I have the following children for George Forbes and Margaret Ross:
Margaret: circa 1780
William: 1781 in Skelbo
Donald: 1783 in Embo
James: 1784 in Embo
John: circa 1787 (likely in Embo)
Christian: 1789 in Embo
Barbara: 1794 in Pronsy
Robert circa 1798
Donald: 1811 in Tulloch, Creich Parish
This last child was born in Creich Parish because his father George was stationed there (likely in case of invasion) during the Napoleonic Wars.
NOTE: THERE WERE NO BIRTH ENTRIES IN THE CHURCH RECORDS AT ALL FOR ANYONE FROM DECEMBER 1740 - JUNE 1744 AND FROM JULY 1751 - AUGUST 1754 AND FROM 1761 - 1813 EXCEPT FOR SIX OR SEVEN FAMILY GROUPS SUCH AS OUR FORBES.
We do have information on some of the children of George Forbes and Margaret Ross. We have visited Scotland numerous times and have stood on the land where they lived - Pronsy Farm and then Pronsycroy just up the road. These are right on the edge of the small town of Dornoch in Sutherlandshire.
Hope this helps. I will include my email in case you want to email again.