Both Nathaniel William Stewart and his younger brother Alexander Vivian Stewart were born in Minigaff, Newton Stewart, in 1891 and 1895 respectively. Both attended Ewart High School in the town, and Boroughmuir Higher Grade School in Edinburgh, with Nathaniel attending the former until 1909 and the latter until 1910.

In session 1910-1911, Nathaniel began studies at Edinburgh University in the Faculty of Medicine, and his brother Alexander matriculated in session 1913-1914 in the Faculty of Science. Nathaniel had excelled in Athletics at the University, and Alexander was in the First XV, Rugby.

As far as the University of Edinburgh Roll of honour 1914-1919 is concerned, Nathaniel's University studies were spread across the arts, medicine and science, 1910-1914. While at University he was a member of the Edinburgh University Officer Training Corps (EUOTC), Infantry, from November 1910 to August 1914, with the rank of Cadet Lance-Corporal. For his part, Alexander too served in the EUOTC, Infantry, from October 1913 to September 1914, with the rank of Cadet.

From the outbreak of the Great War in August 1914, Nathaniel served with the 7th Royal Scots as a 2nd Lieutenant attached to the Royal Flying Corps. He became a Lieutenant in September 1914. In 1916 he served in Gallipoli, before going to Egypt. Nathaniel William Stewart was killed while directing the fire of H.M.S. Fox off Chermwej on Red Sea on 23 January 1917.

From September 1914, Alexander served with the 9th Royal Scots as a Private, then from Decemebr 1916 with the 4th Gordon Highlanders as a 2nd Lieutenant. He fought in France, on the Somme and at Ypres. Alexander Vivian Stewart was killed at the Battle of Arras on 23rd April 1917.