I'll reply to this old post, as I'm sure others are looking.
There is a "Calvin Kellis" in the Kellis family grave yard (behind the old "Center Cemetery", near Biscoe NC.
I'm a decendent of this family.
Back in the day, for what ever reason, no one in this area was looking for a husband or wife who was more then two or three doors down.You can litterally, browse the census records, and see your relatives in order (or is the case with me, lol).
There might have been religious reasons for the "close-knit" family.This might have been the other reason that people backlashed and left the area....everyone was related. I'm actually a foster care kid, etc, however, what turns out to be interesting is that this area is so interbred, that I was actually adopted by relatives, although, they didnt know it at the time.(So, i'm my own distant cousin, and distant uncle).