Jody, I just read your Jan. 8, 2004 posting with great interest. I am assuming that you have access to the Frank Burke Porterfield book, "The Porterfields", which tells us that the Trenton N.J. John Porterfield was the father of the family that emmigrated from Ireland.
I have also raised the question about the oddity in the Will of John Porterfield of Trenton not mentioning a wife or any children. I believe he is most likely a cousin of "our" John who came to America via Ireland. I am amazed that Frank B. Porterfield did not immediately recognize this error. I believe the Trenton N.J. John never married, thus he left his estate to his brother, Alexander at Duchal and newphews of that family.
I have some information indicating that the real John (1675-1738)was born in Ballylennon, Donagel, Ireland. His father William (1645-1681)was born in Stewart, near Sterling, Scotland and died in Ireland. William's father, John Porterfield,(1613-1690)m.Jean Hamilton was born at Duchall Castle and died there. Note that William died 9 years before his father.
Several years ago my wife and I visited Kilmacolm and spent a weekend with the present owners of Duchall, Joe & Winks Maclay (Lord & Lady,that is). Perhaps we can exchange more info. If you do not have the Porterfield book, I believe it can still be purchased.