Hi J. Haynes,
I thought that I would be able to help you out because the name Jeptha Haynes "rang a bell". I have a "Jeptha Haynes" in my family tree database, but he's not attached to the people that you mentioned. I don't have a Gilbert in my database. Also, you didn't mention the years involved.
I had a g-g-grandmother whose name was Mary Frances Haynes (b. 1856 in Jasper Co, Tx). She was the daughter of Dunstan Banks Haynes (b. 1828 in Perry Co, AL) and Mary Ann Horn. Dunston had an uncle whose name was Thomas Haynes (b. 1800 in Green Co, GA.) who married Mary Hurt. Thomas Haynes had a son name Jeptha. Since this was not my direct line, I didn't really continue on it at the time.
If any of this sounds familiar (or promising) or if you want more information on the Haynes and associated families, let me know and I'll help if I can.
P.S. Wiess Bluff IS in Jasper Co.