The info I have on Tarleton Johnson came from various Copeland fanatics. There is an unbelievably huge gang of Copeland researchers, and I am one of them. Tarleton Johnson appears to be a Copeland TWICE. from his mother's side.
Tarleton's mother was most likely Winnifred Da (1794). Her parents were Joseph J Dark and Winnifred Roe. Joseph's parents were Samuel Dark Jr and Agnes Aggie Copeland (1740). Aggie was a daughter of Nicholas Copeland and Nancy Jane Lott.
There's more: Samuel Dark Jr's mother was a Ruth Copeland( 1725)., although I have seen other maiden names for her. It appears that she is from a different branch of the Copeland tree and possibly a great grandaunt to Aggie.
I do not know if Tarleton had any siblings! I have no info on his dad's side of the family. Johnsons are difficult....... as hard as Joneses.
Nancy Jones