He had several distinguished brothers: Alexander Neil, who became Anglican bishop of Toronto; John, Anglican clergyman, dean of the diocese of Montreal and principal of McGill University; James Gray prominent Upper Canada businessman; Donald, an important political figure in Upper Canada.
[1] At the time of his birth his father was stationed with the 1st battalion of the Royal Highland Emigrants on Carleton Island, New York, where Lake Ontario empties into the St. Lawrence River.
Later, after the Treaty of Paris was signed ending the American Revolutionary War the family briefly resided at Fort Oswegatchie (Ogdensburg, N.Y.) before moving to Montreal when Angus was still a very young child.
[1] By 1810, he was working with Alexander Henry the younger and they travelled to Rocky Mountain House (Alta).
Alexander Neil, became bishop of the diocese of Toronto, James Gray was a businessman, Donald was an important political figure in Upper Canada and John was an Anglican clergyman and acting principal of McGill University.