Þorsteinn Guðni Stefánsson was born on March 29, 1917 in Cypress River, Manitoba. He had the last name Johnson in the west.
Spouse: April 14, 1943 Pálína Guðrún Þórðardóttir b. in the Árnes Settlement in New Iceland on July 10, 1914. She had the last name Pálsson in the west.
Children: 1. Stephan Thor b. March 18, 1944 2. Linda Elain b. August 10, 1945 3. Donald Rye b. October 10, 1948.
Þorsteinn was the son of Stefán Guðmundur Þorsteinsson and Sigrún Vilfríður Þorsteinsdóttir, early settlers in the Argyle Settlement in Manitoba. Þorsteinn grew up there with his mother and stepfather, Emil Þorsteinsson. He first worked as a farm hand for Emil but started farming himself in 1938. Pálína was the daughter of Þórður Pálsson and his second wife, Halldóra Högnadóttir, early settlers in the Árnes Settlement.