From variou sources:
Iain or John MacDonald (Iain MacEoghainn Oig (Ewen)) - born in Glen Urquhart, Inverness-shire, Scotland. Died at Bridgeville NS.
Account tells of a grandfather named Ewen escaping from the Massacre of Glencoe in 1692 carrying a young grandson in his arms. John Og MacDonald was said to be that grandson. Another account tells of John [Iain Mac Eoghainn Oig] serving under the banner of Bonnie Prince Charlie at the battle of Culloden in 1746.
A cairn is located on the roadside near Sunny Brae, Nova Scotia dedicated to Iain Mac Eoghainn Oig (John) and his 4 sons.
This MacDonald Family arrived in America in the fall of 1775 as paid passengers on board the emigrant ship Glasgow. on arrival in New York Harbour, the ship was intercepted by the Royal Navy as the American Reviolution had broken out.
Four of Iain [John] MacDonald son's, James, Duncan, Alexander and Ewen [and probably Iain, the father] enlisted in the 2 Batt., Royal Highland Emigrant Regiment in Nov 1775. After the war, the family settled on land grants on the East River of Pictou County, Nova Scotia in the area known as A' Gleann Boidheach [Beautiful Valley]
In 1784, a settlement of disbanded soldiers was made at Pictou Nova Scotia on the East River at the close of the American War. They were, originally, from the Highlands of Scotland.
The names of these first settlers at East River were: Donald Cameron, his brothers Samuel and Finlay, Alexander Cameron, Robert Clark, Peter Grant, first elder in the settlement, James McDonald, Hugh McDonald on the east side of the river. James Fraser, Duncan McDonald, John McDonald, brother of James, John Chisholm, drowned at the Narrows with Finlay Cameron, John McDonald, 2d, John Chisholm, Jr.
John Og McDonald was born at Glen Urquhart and belonged to the Glencoe McDonalds. John McDonald was a grandson or great grandson of that man.
He was about eight years in the Royal Highland Emigrant Regiment, and three of his sons fought with him in the Revolutionary War on the Loyalists' side.
He was married twice. By his first wife he had Duncan, Alexander, Mary and Christy. By his second wife, Margaret Grant, he had James, Ewen, Ann and Ellen.
I am descended from John Og through son Ewen, through Ewens son John, through Johns son, Alexander, etc.
Any further information on this branch would be appreciated, especially the years prior to emigration  from Glen Urquhart