Can't really help. But a couple of things.
Henry Pettis is listed in the Somerset 1798 tax rolls. Looks like he is paying taxes on property, but that there is no dwelling there of yet. This would coincide with the 1800 date of the building of the home.
It stated that from Henry, the house was owned by a John Pettis. Not sure if this is immediately following and would be a son, possibly. Or if this were much closer to the publication on the house that was done in 1934. The owner at present--this in the 1934 historic work on the house...was at the time, William Moore. Perhaps some property records through time might give a clue to the family line that this takes. No doubt there is some connection, but it could be a cousin or uncle to those in your husband's line.
Wish I could have helped more. Have a great day.