Hello Marion - you ask a question on which I have spent many years! I think I have the outlines of an answer, but be in touch directly to sort out details. The THIRD line (my own)is the most recent: John Black of Balephuil (1820-1876) was born out of wedlock in Glasgow to a Tiree woman, Marion McEachern, by a Gaelic-speaking stonemason David Black. In our oral tradition he was a descendant of the McGregors. This John Black lived his life in Balephuil, and the line was called flat "Dubh" in Gaelic. Sons of this line were few, domiciled in Glasgow and Saskatchewan. Also domiciled in Tiree (at Crossapol and Balephuil) was the SECOND line, another John Black, this one born ca. 1775, brought from Lismore ca. 1806 (brought to teach Tiree people how to make fuel out of turf), married to Catherine McLaurin and related to an unpopular factor. They were connected to the Lamont clan. I don't know what their line was called in Gaelic; but his daughter Isabella was accused of being a "witch" who caused the terrible Fuadach storm in 1856, so you can imagine how unwelcomed they felt. Most of them moved on to Glasgow. The FIRST line is the one you mention, which according to my Tiree and Glasgow relatives claimed to be indigenous, but which was known to be connected to the Blacks of Mull (the south coast, I seem to recall) and thus attached to the McLean clan. These were domiciled at Gorten-vic-Eachainn and Kenovay, in Tiree, and some few came to Wellington and Bruce Counties (Ontario, Canada) in the 1848 emigration. I think there are still some in Tiree, and that they are or were "McIldowy" (Mac ghille duibh) in Gaelic. (There were some there in 1974, anyway!) Tiree people I found close-mouthed and secretive, and this is about all of what I have distilled after 33 years of intermittent effort.... Sigh.