One theory is that William was a son of Hans Georg Kersh, who imigrated from Germany via Rotterdam to Charleston SC about 1741. William and another son was born in SC and for some reason changed name to Kearse. If this is in fact your ancestor, he married Flora Brabham and then Elizabeth McMillan. There is a lot of info on the family in Mizpah: A Family Book, by Rev. M.M. Brabham. William served as capt in James Jones' Volunteer Militia, SC Provincial Troops.