Edgar family

[soapy1]

I have a Mary Edgar who married William Burnet  in 1820 in Middlebie. He was my gggg uncle. They went to Canada with their children. She died there 1861, and he died 1866 there. I'm trying to find her parents, without much success. I found a Sibella Edgar who was married to a James Burnet and wonder if the two are related at all. They seem to have stayed in Stableton and both were buried in Dornock Cemetery.Sibella was born appr 1704. and per the headstone died 1775, James died 5 July 1760 aged 85, per the headstone. I went to the Scotlands people Centre , but couldn't find any of them
Anyone got any ideas? any help would be appreciated as i'm getting to those wee brick walls and try as I might, i can't find info