Duncan

Duncan was a human who lived in Scotland in the 18th century. He was a friend or relative of Seamus MacIntyre.

In 1746, Duncan was a member of the Scottish forces in the Jacobite rebellion. He and his comrades came to the rescue of Seamus, the time-lost Montgomery Scott and Seamus' future wife Megan when they were trapped in a cabin by English officers, all of whom were killed by Duncan and his group. Seamus, Megan and Scott then accompanied Duncan to Inverness. 

Duncan's precise relationship to Seamus is never specified.