Angus Òg had two sons, both named John or Iain, one legitimate, the other natural. From the natural son, known as lain Fraoch, i.e. John of the Heather, or Iain Abrach, from his having been fostered in Lochaber, are descended the CLAN IAIN ABRACH or MacDONALDS of GLENCOE, whose Chief was known by the patronymic MacIAIN.
Angus Òg's elder, legitimate son, also named John, added greatly to the already vast possessions of the family, largely through his marriage to his distant cousin Euphemia (Amie) MacRuairi, whose only brother Ranald was murdered by the Earl of Ross at Elcho Nunnery in 1346: and left no heirs.
John of' Isla, as the family were now designated, was the first of his line to assume the title of LORD OF THE ISLES which although not at that time recognised by the Scottish Crown, almost accurately reflected his position in the Gaelic-speaking Western Highland and Isles.
John held court, appointed his own heralds, ran the government of his domains through the Council of the lsles, built monasteries and generally acted in the manner of an independent prince, whose authority was absolute.
He patronised the Gaelic bards and thereby preserved the culture of the Gael. For his benevolence to the Church, John earned the soubriquet of "Good John". It is probable that John 's first wife, Amie MacRuairi, whom he had married in 1337, died, perhaps in childbirth, sometime prior to his second marriage in 1350 to Margaret, daughter of Robert, the High Steward of Scotland, who succeeded his uncle, David II as King of Scots in 1371 by the title of Robert II and adopted the surname of Stewart, derived from his former "office". One of the first acts of the new king was to grant to his son-in-law, John of Isla, a charter of the former MacRuairi lands, which comprised the Lordship of Garmoran in western Inverness-shire, the Isle of Eigg and the Outer Hebrides. The following year, 1372, John granted to Ranald, the eldest surviving son of his first marriage to Amie MacRuairi, a charter of most of the former MacRuairi lands to be held of the eldest son of John's second royal marriage with the Princess Margaret Stewart.
