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This tree is a reconstruction of the MacDonald / McDonell family tree focusing on the Keppoch branch of the family (of R1b M222 S588 S7814). Many genealogical trees trace the Lords of Keppoch from Alexander of Lochaber a brother of Donald II Lord of the Isles (b. 1363 r.1387-1423) rather than his son Alexander IV Lord of the Isles ( b.1402 r. 1440-1449) and Earl of Ross (1423-1449). The 2nd Lord of Keppoch was Angus Mac Alexander McDonell and his father Alexander was listed as the first Lord of Keppoch in the genealogies. He was mistakenly identified with Alexander (brother of Donald II) rather than Alexander (the son of Donald II). Alexander and his uncle Alexander have been confused and they both were Lord of the Isles during the same period. Donald's brother Alexander III succeeded him as Lord of the Isles (r.1423-1440) and Alexander IV became the Earl of Ross [by right of his mother Lady Mariota of Ross (b. 1382)] and then in 1440 on the death of his uncle Alexander III, he became the Lord of the Isles as well.
The male line of Hugh McDonald of Sleat is R1a ydna whereas the male line of Donald II of the Isles is R1b M222+. Alexander IV Lord of the Isles was the first husband of Hugh of Sleat's mother Elizabeth (nee Seton) the widowed Lady of the Isles (b.1416 d.1479) who married his father Alexander 4th Lord of Glengarry of Clan Ruari (d.1460) soon after her first husband's death. Hugh of Sleat was born in 1452 and died around 1498. Hugh's maternal half brothers were John III 12th Lord of the Isles (b.1434 r1449-1480) and Angus McDonell 2nd Lord of Keppoch. He also had full brother John Ranaldson MacDonald (b.1450 d.1501) 5th Lord of Glengarry of the Ruari Clan.
Donald II also had a son Duncan who married Roberta the heiress of Glenerochie who was a daughter of Robert de Atholl. They were the ancestors of the Robertson Clan Chiefs (of R1b M222 S588 S603 y-dna). It is from their son Robert Riabhach that the surname of Robertson derives.
Many of the histories of this family were not written until the 17th century a couple of hundred years after many of the events so certain information was inaccurate or partially correct. The history and genealogies of these families are in need of reconstruction in certain aspects. Using the genealogies, historical research, legends and dna evidence can aid in this reconstruction.
Note added 18 October 2017: It would also seem that the S603 Ferguson families descend from Robert Riabhach (Ruadh) and that this surname was most likely first found in a grandson or great grandson of Robert. see Ferguson Project