The only George I have seen was a George W. Cain, born about 1819 in Marion County, SC, and died before 1869. He was a son of Lawrence Larry Cain (one of the O'Cains who changed his name to Cain.)
George W. Cain's mother was said to be Delilah. (Her maiden name may have been Exum.) His wife was Sophia Hutchinson, according to the 1860 census. They had no children at that time, but later had a daughter Sarah A. Cain.
She was born 1860 and died 1933. Her husband was James Wilson Lundy.

This information is in the book The Cain Tree and Tangled Branches by Sadie Leach Hegg.
Also a great deal of Cain/O'Cain information can be found at the Three Rivers Historical Society in Hemingway, SC.
I hope that this helps you.
I am not sure if the Marion County O'Cains are related to the ones in Orangeburg, SC.
Susan