Clan Stewart of Appin is a west highland

Scottish Highlands

The Highlands is an historic region of Scotland. The area is sometimes referred to as the "Scottish Highlands". It was culturally distinguishable from the Lowlands from the later Middle Ages into the modern period, when Lowland Scots replaced Scottish Gaelic throughout most of the Lowlands...

 branch of the Clan Stewart and have been considered a distinct clan

Scottish clan

Scottish clans , give a sense of identity and shared descent to people in Scotland and to their relations throughout the world, with a formal structure of Clan Chiefs recognised by the court of the Lord Lyon, King of Arms which acts as an authority concerning matters of heraldry and Coat of Arms...

 since the 15th century. They are descended from Sir James Stewart of Perston, who was himself the grandson of Alexander Stewart, 4th High Steward of Scotland

Alexander Stewart, 4th High Steward of Scotland

Alexander Stewart was 4th hereditary High Steward of Scotland from his father's death in 1246.A son of Walter Stewart, 3rd High Steward of Scotland by his wife Bethóc, daughter of Gille Críst, Earl of Angus, Alexander is said to have accompanied Louis IX of France on the Seventh Crusade...

. (See: High Steward of Scotland

High Steward of Scotland

The title of High Steward or Great Steward was given in the 12th century to Walter Fitzalan, whose descendants became the House of Stewart. In 1371, the last High Steward inherited the throne, and thereafter the title of High Steward of Scotland has been held as a subsidiary title to that of Duke...

).
The Appin Stewarts, also known as “The Loyal Clan”, is the West Highland branch of the royal surname Stewart, descend from Sir James Stewart of Perston, 4th son of Sir John Stewart of Bonkill

John Stewart of Bonkyll (d.1298)

John Stewart of Bonkyll was a son of Alexander Stewart the High Steward of Scotland and Jean, daughter of Séamus Macrory, Lord of Bute. He was a military commander during the First Scottish War of Independence and during the Battle of Falkirk, he commanded the Scottish archers, and was killed on 22...

, second son of Alexander, the 4th High Steward of Scotland.