He was my Great Great Grandfather as well. My sister & I have I have information from other family members still residing in NC that reflect the same information posted, family rumor from my Mother is that his father was Native American.
I believe there was an enlistment document that listed him as having green eyes / brown or black hair(?) & race as mullato. I saw it on Ancestry.com.
I am not able to find evidence of Mary ever getting married, or having other children. Noticed she did live with her brother in some census, in different years. I think once George was with her at her brothers when he was very young, if I recall correctly.
Our family branch, at least, has some very strong native type traits that were very prelevant in my mother (who had black hair & green eyes), my sister & my eldest son. I never met my grandmother and the photos I remember were from when she was very elderly and hard to remember.
We were thinking of trying to trace the family he was with, perhaps they know something? Because he does not seem to return to the Sykes family, from what I can tell.
Please let me know if you can find out any further information because George seems to be a BIG question mark. At least we now know that some other cousins are wondering as well. I will update if any info dug up.