Daughter of Count Adelin Le Grelle and Rosalie de Swert, Countess Marie-Antoinette was the cousin of Cécilia Sarkozy, the second wife of former French President Nicolas Sarkozy. In 1944, at the liberation of Antwerp, she met Keith MacLellan. Like many young people of his generation, MacLellan had been forced to interrupt his studies during the war and joined the Royal Montreal Regiment, with whom he trained, was appointed an officer and sent to the United Kingdom, where he was transferred to the 1st Special Air Service (1st SAS). He became one of only two Canadians to serve in the 1st SAS during the war. At that time, he was part of small, jeep-mounted units operating behind enemy lines in Belgium, the Netherlands, Germany, and Norway. After the war, on 11 September 1946, Marie-Antoinette married Keith MacLellan while he was a student at Oxford. An ambassador to many countries, MacLellan was a Canadian diplomat who helped shape Canada's multilateral foreign policy after the war and championed the cause of a united federal Canada.