Hi Janae! As it turns out Steven Yowell has possibly solved the mystery of O.T. Yowell. It's probable that O.T. was actually O.P."Happy" Yowell and may very well have known O.T. Cain, or even that the writer of the book I mentioned got the initials of the two confused. I don't have any Cains in by database, but if you have the opportunity to scan the photo of your great-grandfather with the oil rig, I'd love to have a copy.