Jane Haining's last will and testament was among treasures found in a church archive in Edinburgh earlier this year.
The Church of Scotland said that the newly discovered will was found in an attic space alongside 70 photographs, a ring and letters belonging to the heroic Christian.
Haining died at the Auschwitz concentration camp in 1944.
The Dumfries native had been working as a school matron in a Church of Scotland school in Budapest when Hitler came to power.
At the time, Budapest was almost 60 per cent Jewish in population.
The Church of Scotland school was renowned for treating both Christian and Jewish children equally, according to a 2014 BBC documentary about Haining's life.
After the declaration of war in 1939, Hungary's government aligned itself with Germany.
The Church of Scotland were concerned for their missionaries based in Budapest and wrote to Haining to recommend that she return home.
In her response Haining wrote: "If these children needed me in days of sunshine, how much more do they need me in these days of darkness?"
Haining was sent to Auschwitz in 1944 after being arrested on suspicion of "espionage on behalf of England".
As a political prisoner, she was screamed at, beaten and chased with dogs.
She survived two months at the camp and passed away at the age of 47.
After the discovery of her will, the Moderator of the General Assembly, Right Rev Dr Russell Barr, hosted a reception with 14 of Haining's relatives.
Joyce Greenlees, whose grandfather Harold Haining was Miss Haining's cousin, met a number of family members for the first time.
Greenlees, a retired primary school teacher, said: "I am so proud and pleased to meet members of a family I did not realise existed.
"Jane Haining was a very brave lady who was totally selfless, and I think it is very important that everyone knows her story because we can learn lessons from the fact she deeply cared about all people, regardless of religious belief."
Haining is the only Scot to be officially honoured at the Yad Vashem memorial in Israel for giving her life to help protect Jews during the Holocaust.
Memorials to her life and dedication to peace and tolerance can be found across Hungary.
A stained glass window is dedicated to her at the Queen's Park Church of Scotland in Glasgow where she was once a member.