@GRob81, I think Tara also asked earlier, what brought you to focus on and/or believe that Robert's father was a David, when no name is mentioned on Robert's marriage?
Was it oral family history, handed down over the years, or is there any written source (official record or otherwise), for it?
Just to keep all possibilities open at moment, have you given any consideration to Robert having been born to an unmarried Robinson (or otherwise), female?