Looking for family of my great-grandfather

My Great-grandfather was Rev. Douglas Harrison 1821 - 1901. He was born in Fairfield County South Carolina and was married to Aurelia Patterson. Aurelia's name is sometimes misspelled as Amelia. My grandfather, William Plummer Harrison, insisted the family was connected to President Wm Henry Harrison (I was too young to ask questions then & now it is too late). Does anyone have information on Rev. Douglas Harrison (Ordained Presbyterian minister about 1856). Any information will be greatly appreciated.

Harrie Nell HARRISON