The chapter entitled the Riddles of Sipsey River can be found at the end of the book Warrior Mountains Folklore written by Rickey Butch Walker. I purchased the book from Blount County Memorial Museum and Historical Society in Oneonta,AL Unfortunately it seems to be more folklore than facts. Rake Riddle for example is presented as a full blooded Cherokee, and many of the Riddle cousins either identify themselves as Indian or are listed as such. From my understanding, relative DNA does not support that theory. These were a wild and angry bunch though so I wouldn't have argued with them at all either.
There are theories about this group referring to themselves as black dutch (and also black foot indian) to deter questions of mixed blood, and some interesting reading on Melungeon people that lived and traveled together which may have been offspring to the lost colony of Roanoke. Families of Riddle, Bunch, Mullins and a few others named.
I'm sure your records and research can shed some light into accuracy of some of this info. Good Luck and let me know if you have specific questions.
Thank you,
M. Cloer McClellan