Wallenberg's mother Maj von Dardel and his stepfather Fredrik von Dardel made relentless attempts after the diplomat's 1945 disappearance to gain information about his whereabouts and secure his safe return.
Family archives, large parts of which have been viewed for the first time by the Wall Street Journal, bear witness to an increasing sense of desperation on the part of the elderly couple.
On February 12th 1979, Fredrik von Dardel, aged 93, took an overdose of sleeping pills and died in his bed. Two days later, 87-year-old Maj von Dardel was found dead on her sofa after swallowing an overdose of barbiturates.
Raoul Wallenberg helped prevent thousands of Jews from being sent to the Nazi concentration camps after moving to Budapest in 1944 to work with the US-run War Refugee Board.
He was taken prisoner by the Soviet Union in 1945 and his fate has never been revealed.