Trooper Sinclair was born on August 11, 1917 in Punnichy, SK to parents Jim and Harriet Sinclair. Before enlisting, he worked as a mechanic. Travelled to Saskatoon in May 1941 to enlist with the 1st Canadian Armoured Carrier Regiment R.C.A.C.
On April 11th, 1944, Sinclair was involved in a fatal automobile accident and sustained severe fractures to his skull. He was transported to a military hospital in Serracapriola, Italy, where he later succumbed to his wounds. Survived by his four brothers and three sisters.