Welcome to my roadblock. There are a couple of researchers who have been looking for William for a while. I think his name was William Allen Shepperd Sr or 1st. Just a speculation based on statements in his will. If you get information at this forum, it will fill in blanks on several family trees.
Another of my blocks is Robert Alexander's wife Lousia Ann Hagen. I think she was William Beaureguard and Thomas Cogdon Hagen's sister, but can't say for sure. They came to Texas at about the same time and also left Upshur County at about the same time. Bell County Historians list the Hagens as coming there with the Shepperds and Andersons. (It doesn't help any that William Beaureguard Hagen named one of his daughters Louisa Ann, especially since they were all in the same place.) Do you have any definitive information about her? She and Robert were my great, great grandparents.