Hi Rose
Did I previously send you what I have on your family? I will email it again just in case.
Duncan Mackay said to have married his cousin Janet Mackay is interesting. Janet is the daughter of Barbara Mackay and Donald Mackay. Barbara is the daughter of Adam Mackay and Mary Murray of Gruids, Lairg. They did not have a James as far as I know which means that the siblings who create cousins have to be James Mackay and Donald Mackay. At least it narrows it down a bit. There is a lady in New Zealand who is descended from Adam Mackay - I will email you her address.
Hope this helps.
Christine