Marla:
What exactly did your cousin find and in what form? Everyone in the family described origins in Scotland, specifically, as I understand, South Uist. There was a discussion once of their putting in to Wales for a time, but not actually living there long term. I also recall bits of Gaelic being spoken, even by my grandmother as I grew up and have an old bible from "back home" dated 1807 and in Scots Gaelic. Apparently, at least for a time, they corresponded with relatives remaining behind. The National Genealogist for Clan Donald also has some similar Isaacks listings. Could it be that your cousin found evidence of their stopover in Wales? The secret lies, I think in something around 1716. Some event, supposedly in the Western Isles prompted the decision to emigrate. An intriguing issue, at any rate.