After searching for over 10 years for parents of John Blakely (born 1783/1786 in SC) who moved to Mississippi about 1818 and married Elizabeth Smith I think that I have found them. They are Dionysius and Fanny Blakely of Lexington and later Edgefield counties in South Carolina.
In Dionysius’s probate in 1815 he has a son named John. He had two sons under 16 on the 1790 census. The probate also lists John Hidle (husband of Mary Blakely who was a daughter of Dionysius); they had a son John B. Hidle who was born in 1821 in South Carolina.
On the 1860 Newton county, Mississippi census there is a John Hydle (age 39 & born in SC) living in the household with John Blakely. I believe that this John Hydle is the nephew of John Blakely.