Benjamin was my GGgrandfather via his son William Morrow Wiliams. You can view his data at
https://www.familysearch.org/tree/person/details/LCTR-NL2. He emigrated to Delaware Co, Ohio in approx. 1833. I *might* have found the immigration record (and naturalization certificate from 1844), but Welsh males had only about 10 given names and no middle names, so there are multiple records of Benjamin Williamses and possible relatives all over the Internet. I have a possible record of Benjamin, Phoebe, and his son David showing his residence as Galena, Delaware Co, Ohio in the 1840 census. Unfortunately, that census only names the head of the household, but the ages and family composition at that time fit.
It's not clear to me that Thomas and Ann made the trip with Benjamin. I can't find anything definitive about their life or death in Ohio. I have been corresponding with an Alan Hughes in England, who is related to Ann Jones. Two items of interest:
1."Birth [of Benjamin] recorded in the records of Gyffilliog Calvinist Methodist Church, with parents as Thomas and Ann."
2. "I believe Benjamin's parents both died in the 3rd influenza epidemic that swept through much of the UK at that time, it lasted over 13 months! The social status determined the percentage chance you had of surviving, the poorer you were the less chance you had! The Williams family were historically of servant stock, we have historical evidence of them back to the 14th Century (but not a direct lineage at this point in time)."
Concerning the possible parentage of David Williams and Anne Powell, that is based in part on a brief bio of their son Ebenezer in "History of Delaware County and Ohio. Containing a brief history of the State of Ohio" (
https://archive.org/stream/cu31924050611106/cu31924050611106_djvu.txt). I suspect that they *might* have been Benjamin's uncle and aunt, and that Benjamin emigrated with them, possibly after his parents died. But again, there were so many immigrant Williams males with the same name in those days, it's hard to pin down an association.
That's the best I can do for now.