Wallenberg was last seen in Budapest, Hungary, on January 17, 1945 when he was arrested by Soviet officers during the final months of WWII.
He disappeared after that though Russian officials said years later he died in a Moscow prison in 1947 from a heart attack. In 2000, a Russian investigation claimed KGB agents shot Wallenberg in 1947.
His surviving relatives have long remain skeptical about what happened. On Friday, family members said in statement sent to news agency AFP that a "declaration of death is a way to deal with the trauma we lived through".
"The family has lived in hope and despair, hope that their efforts would bear fruit and Raoul would return, despair as their hopes were dashed again and again... We have now decided to lay Raoul to rest and are planning a memorial site," the statement read.
While stationed at the Swedish Embassy in Budapest, the Swedish diplomat saved the lives of hundreds of thousands of Jews by issuing them documents which looked like Swedish passports.