John was the son of
Aonghus Óg Mac Domhnaill, an
Islay-based nobleman who had benefited from King
Robert I of Scotland's attacks on the
MacDougall (
Mac Dhùghaill) rulers of
Argyll and their Comyn allies, and had been given
Ardnamurchan,
Lochaber,
Duror and
Glencoe, turning the MacDonalds from the Hebridean "poor relations" into the most powerful kindred of the north-western seaboard. The loyalty of Aonghas to Robert, however, did not mean that John's loyalty to Robert's son and successor
David II would follow suit. After
Edward Balliol's coup against the Bruce regime in 1333, Edward attempted to court John. In 1336, Edward confirmed the territories which the Islay lords had acquired in the days of Robert I; and additionally, Edward awarded John the lands of
Kintyre,
Knapdale,
Gigha,
Colonsay,
Mull,
Skye,
Lewis, and
Morvern, held by magnates still loyal to the
Bruces. John, however, never provided Edward with real assistance. Although Balliol's deposition by the supporters of David made the grants made to John void, John's pre-1336 possessions were confirmed by King David in 1343. Moreover, in 1346, John inherited the great
Lordship of Garmoran through his marriage to
Amie mac Ruari after the death of her brother
Raghnall Mac Ruaidhrí. This meant that John's dominions now included all of the Hebrides except Skye, and all of the western seaboard from Morvern to
Loch Hourn. John continued to build his power base by allying himself with
Robert II of Scotland, another West Highland magnate who was the designated heir of King David. After David went into English custody in 1346, Robert acted as the
de facto ruler of Scotland north of the
River Forth. In 1350, John was given Robert's daughter Margaret Stewart in marriage, and received Knapdale and Kintyre as dowry. However, Robert was the senior partner, and John had to divorce his first wife Amie; his sons Godfrey, John and
Ranald by Amie were to be passed over in the succession in favour of any children by the marriage with Margaret. After the capture of the king and death of
John Randolph at the
Battle of Neville's Cross in 1346, John and Robert worked together taking control of the huge
earldom of Moray, bringing MacDonald power into
Lochaber and Stewart power into
Badenoch. David returned to Scotland in 1357, and resented these incursions into an earldom which David regarded as within his rights of disposal; the terms of the original grant of Moray to
Thomas Randolph in 1312 stipulated that the earldom would revert to the Crown upon lack of issue. By 1368, King David had decided that an aggressive policy was needed in the north. In 1369, he marched to
Inverness, where John submitted to his authority. John's submission, though, was followed swiftly by David's death on 22 February 1371. David was succeeded by John's close ally Robert. David had wished either to retain control of the earldom or to grant the earldom to either John or George Dunbar, the sons of
Isabella Randolph, sister of the last earl. However, King Robert made sure that Badenoch remained within his own control and that John kept Lochaber. When the earldom was granted to John Dunbar by a parliament held at
Scone in early 1372, the grant consisted only of the lowland part around Inverness. Robert also ensured that John's control of the Mac Ruairidh inheritance was legally recognised by charter, and in 1376 issued charters confirming John's control of Colonsay, Kintyre and Knapdale, and granted Lochaber to John and his Stewart wife together. Soon after 1376, John's heir
Domhnall may have been the
de facto ruler. John lived until 1386, when he died at
Ardtornish Castle in Morvern. He was buried in
Iona. John's power had been built on both the loosening of royal authority in north-western Scotland after the
First War of Scottish Independence and, more importantly, on allying with the right people at the right time. The success of John was so great that his successors could maintain a distance from the Crown that outlived the weak monarchy of the 14th century. John was also a great cultural and religious patron. Although the
Bishop of the Isles, based at Snizort on
Skye, was outside his control and to some extent acted as a political rival, John did control Iona, the spiritual homeland of Scottish Christianity. The monastic establishment of Iona was run with John's approval by the
MacKinnon (
Mac Fhionnghuin) kindred. John also founded an
Augustinian priory at
Oronsay, an act unique in the period. ==Marriage and issue==