1. The book about Isaac Ross and Jean Brown by Wright says that the parents of William Ross of Martin County, NC were Hugh Ross and Margaret of Elizabeth City, Virginia. Margaret remarried James Priest in 1702 by a marriage bond in Elizabeth City, Virginia. In 1719 Margaret Priest had a will in Elizabeth City that mentions sons Francis, Hugh, and William. Wright says that Isaac Ross is not directly related to William Ross of Martin, but perhaps over the oceans. Thus not brothers.
And a book including the Rosses of Martin County, Dickerman's House of Plant, 1900, online towards the end of the book says Hugh Ross and Margaret of Virginia could easily be the parents of William Ross of Martin. Dickerman was as was Wright a genuine family scholar.
2. Isaac Ross, James P Ross, and William Ross of Martin NC, listed as brothers do seem related (and that is an important observation) and they were in the same places. But Isaac Ross is not on the will of Margaret (Ross) Priest, 1719, Virginia, nor is James P Ross. They would have to be cousins of some sort.
I propose Francis Ross, Hugh Ross, ll, and William Ross of Martin as children of Hugh Ross. And Isaac Ross and James P Ross as cousins to some degree or another.
2. New but old stuff is online now. James P Ross seems to have had a son Francis Ross in Rowan who warranted land in Rowan in 1759 (MARS Catalog of NC) and was on the 1770 and 1780 census of Rowan. This matches with this family of Hugh Ross in Elizabeth City, Virginia. A John Ross was dcd in 1758 in Hampton, Elizabeth City, Virginia and mentions his brother James. I think that is probably James P Ross. No-one has been able to find such a source in Ireland and we now know this Ross familly migrated over the border into Northeast, North Carolina. The father of John and James would be Francis Ross by other things on the will, etc.
3. Isaac Ross according to Wright started in Woodbridge, Middlesex, New Jersey and went through Virginia to Rowan County, NC and later to Mechlenberge NC, near the SC border. Two of his sons were on a deed in Granvilles, NC next to Rowan in 1762, two years after Isaac's death
What is interesting about this is that my own John Ross of Guilford by timing of events and comparison of signatures left Elizabeth City Virginia and was married in Woodbridge, Middlesex, New Jersey in 1759, not to be confused with the other John Rosses of Middlesex. After that he returned to Virginia and was in Granville in 1760, the same granville as the sons of Isaac Ross.
And in Mechlenberg were some of the descendants of William Ross of Martin (Dickerman).
But what is also interesting is that this Andrew Ross, Surgeon (above post) who sold the Balblair property by the Colonial Families of Philadelphia was in Edinburgh and in Kingston, Jamaica. In Piscataway, Middlesex, NJ was Alexander Ross, who knew George Washington, whose residence was used as command station by George Washington (Wikipedia). Alexander Ross by the History of Middlesex was a Physician of Kingston Jamaica and was from Scotland. In the 1775 will of Alexander Ross in Middlesex, New Jersey he mentions his Jamaica property, sister Jean Ross, and John Ross of Philadelphia as handling some money to sister Jean. In 1777 the will of Jean Ross, "presently of New York" mentions Brother Alexander Ross in New Jersey, the Jamaica property, and John Ross of Philadelphia as one of the Ex's of her will.
4. This gives a connection of James P Ross, who was also in Rowan, Isaac Ross, William Ross of Martin, John Ross of Guilford, Hugh Ross and Margaret of Elizabeth City, Virginia, and lastly the
Balblair Rosses of Scotland, by way of two sons of David Ross and Margaret Stronach in America. That is John Ross of Philadelphia, son of George Ross, and by Andrew Ross, who had descendants in Middleses, New Jersey. The Piscataway and Woodbridge Rosses were connected by data.
I think Isaac Ross is more likely a son of Andrew Ross, son of David Ross and Margaret Stronach than of son Hugh Ross of the same.
A second connection besides all these associations is on page 22 of the 1882 book, Life and Times of Elder Reuben Ross, grandson of Hugh Ross and Margaret, that has a tradition that the Martin County Ross were directly from Scotland, and migrated to Pennsylvania and Maryland. And that they Scholars, Statesman, Navigators and Warriors.
5. Hugh Murdoch Ross is not mentioned by Reed in the book, the Earls of Ross and Their Descendants as being on that line. The one he mentions was dcd by 1702 in Scotland and was too old by my calculation of a sasine inheritance.