Fran, I don't think we know enough either way to determine if your great grandfather John or my Phoebe were related to the John I mentioned in the original posting. Can you find your great grandfather in the 1850 census with his parents? Any clue as to where he was born? That's all the hope I can offer you at this point.
My Phebe was born in 1790, married in 1811, died in 1853, so she was not listed on any census with her parents. My thought in posting the information and request about John was that maybe someone knew how many children he had and what their names were. Otherwise I'm going to have to locate and research the will of every Piersall in Virginia.
If I find out any more on either one of these people, I'll let you know. Please do the same for me.