Donat Coste was born Daniel Boudreau on 12 January 1912, in Petit-Rocher, New Brunswick, to Joseph and Marie Roy Boudreau, who had moved there from Lamèque, New Brunswick. He was the grandnephew of Jérôme Boudreau, the first French-speaking school-teacher in the province, and one of the three brothers of Eddy Boudreau, a well-known journalist with L'Evangéline, the Acadian newspaper, and author of La Vie en croix (Life on the Cross, 1948) and Vers le triomphe (Toward Triumph, 1950).

The Boudreau children were orphaned in 1917, and Daniel was adopted by the French industrialist J.-Edouard Coste, from the islands of Saint-Pierre et Miquelon. He received his early schooling in Saint-Pierre (1918-1927) and in Montreal (with the Frères des Ecoles Chrétiennes and the Abbé Adolphe Poisson, 1927-1929), where the Coste family had settled. Having been awarded a scholarship to study at...