The earliest record I have found of William Corson was in the 1841 census for Parton, William (age 12) was living at Parton Manse with his sister Caroline (age 10), they were both said to be "Supported by Parish".
Ages shown in the 1841 census are not reliable, so where possible, I have calculated years of birth from ages recorded on Marriage and death certificates
I have not found any BMD documents to confirm that William was the son of William Corson and Grace Gourley. However, I have a DNA match with a descendant of William Corson and his wife Agnes McVane which can only have come from William Corson and Grace Gourley through their daughter Isabella and son William.