Have made some progress on this line, possibly. After reviewing the 1796 Flax Bounty List I think that a connection to a Joseph Hart might be possibla. Joseph was listed on the Bounty List as in Loghgilly County Armagh. This ties in to Isaac always being identified as a farmer in the U.S.
Indicatiopns are that Isaac was Presbyterian. This comes by his marriage in 1817 in Baltimore Maryland. The weddinf rook place in a Presbyterian Church there in Baltimoer. I also think ?I found the Baptimal recrord for who would become his wife. Mary Carother (Caeeuthers) was baptised March 129, 1799 in Anahilt Presbyterian Parish in Glogher County Down. Unable to find any wedding or funeeral record for her in Ireland so think this might be the correct one.
So far all my searches on Isaac, his brother Jacob and their sister Betty (Elizabeth) have turned up empty. I can't seem to connect them to any one else in County Armagh. Is there any place else that far back I can check? It is too early for the valuation. They don't show n any Flax list. I didd fijnd one site that seemed to have many ship passenger lists. It might have them back and forh to Scotland. I already checked it for 1817, the year Isaac says he came to the U.S., and find nothing for the entire year.