Jan Kostanski was the son of Wladislawa Kostanska. He was born June 24, 1925 in Warsaw and had two younger sisters, Jadzia and Danusia. His parents divorced when he was a child, and he was raised by his mother. Until 1940 the family lived in the old city of Warsaw. Due to the destruction caused by German bombing, they were forced to relocate to the commercial district near the Mirowski market. In their new apartment house located at 9 Mirowski Square, they befriended an extended Jewish family by the name of Wierzbicki, some of whom lived across the courtyard in the same apartment bloc. The family consisted of the widower, Ajzyk Wierzbicki, his elderly parents, his son Nathan and daughter Nacha, his brother Berek and Berek's wife and children, Fela and Jakob. The families became so close that Jan considered Ajzyk his stepfather and Ajzyk's parents, his surrogate grandparents.
When the Germans built the Warsaw ghetto wall in 1940, the apartment house at 9 Mirowski Square was divided in two, with the Kostanskis on one side and the Wierzbickis on the other. Immediately after the sealing of the ghetto in November of that year, Jan (with the support of his mother) began sneaking into the ghetto in order to help the Wierzbickis. Soon both families became instrumental in a large-scale smuggling operation to bring food into the ghetto. At first smuggling was conducted over the ghetto wall. A few Jews would stand on a ladder and extend a rope with a hook over the wall while Poles would help hoist bundles of supplies over the wall. In this manner 15-20 pounds of goods could be transferred in an hour. Much of this activity took place in the Mirowski marketplace, where the transfer of goods was less noticeable. In addition to his smuggling efforts, Jan made frequent visits to the ghetto in order to maintain social contact with the Wierzbickis. One time he even arranged to take Nacha out of the ghetto to see a movie. Later, when the Germans moved Jews out of the apartments which bordered on the ghetto wall, smuggling became much more difficult and fraught with danger. On one occasion while transferring goods through the neutral zone of vacated apartments, Jan and a group of approximately fifty Jewish boys were arrested during a raid. The Jews were executed, but Jan was released after his mother paid a substantial bribe to a Polish policeman. She claimed that her son had only entered the ghetto in order to retrieve a ball that he had accidentally thrown over the wall.
Shortly before the onset of the mass deportations of the summer of 1942, Jan was asked to help transfer a secret archive of ghetto photographs taken by a Jewish photographer, known as Edek, to the Aryan side. Edek, who was a friend of Jakob Wierzbicki, had a permit from the Germans to have a camera in the ghetto in order to take photos of Jewish corpses at the cemetery before they were buried in mass graves. In addition to these official photographs, he also took many unofficial pictures to document the true nature of life in the ghetto. Among those images were pictures of the smuggling operation. Unfortunately, Edek was rounded-up for deportation before the transfer was made, and his archive did not survive apart from a few images he had given to friends.
Jan's mother was determined to rescue the Wierzbicki family. However, she could arrange hiding places for only Ajzyk, Nathan and Nacha. She hoped to be able to help more of them later, but the grandparents were elderly, Fela was in her eighth month of pregnancy, and Jakob was unable to pass as a non-Jew, and in any event, was unwilling to abandon his parents. With the help of Wladek Cyrkiert, a Jewish youth who was living in hiding on the Aryan side, Jan re-entered the ghetto and brought out the three Wierzbickis. Each was escorted separately to the home of his Aunt Irka in Praga. They were able to remain there only a short time before arousing the suspicion of the neighbors. As a result, Jan decided to smuggle them into the still peaceful Otwock ghetto until other arrangements could be made.
Soon after their arrival, however, rumors circulated about the ghetto's impending liquidation. While Jan's mother searched desperately for a new apartment where she could hide the Wierzbickis, the round-ups in Otwock began and the Wierzbickis were put on a deportation train to Treblinka. They managed to escape, however, and returned on their own to Irka's home in Praga. While Wladislawa continued her hunt for new quarters, Jan arranged to smuggle the Wierzbickis back into the Warsaw ghetto, where the deportations had stopped temporarily. Upon their return they learned of the death and deportation of the other members of their extended family. Jan continued to visit them in the ghetto despite the high risk of capture.
In January 1943, Jan's thirteen-year-old sister Jadzia, was caught in a German raid at a Warsaw cinema and deported to Majdanek. She was released in a weakened state several weeks later after her mother paid a substantial bribe to secure her freedom. During her internment Wladislawa finally found a suitable apartment for themselves and the Wierzbickis and constructed a secret room where they could hide. Soon after, Jan and Wladek returned to the ghetto and brought out the Wierzbickis. Wladek also came to live with them. From the safety of the Kostanski home, Ajzyk, Nacha, Nathan and Wladek witnessed the destruction of the Warsaw ghetto. For the next eighteen months Wladislawa and Jan went out daily to trade goods in order to support their enlarged household, while Jadzia kept house and Nacha cooked. The Kostanskis were avid supporters of the Polish uprising when it finally occurred in August 1944, but they kept their efforts focused on protecting the four Jewish members of their household. After the collapse of the insurrection and the forced evacuation of the city, Jan's mother and sisters departed, leaving Jan to care for the hidden Jews. They found shelter in a series of cellars concealed by the rubble of destroyed buildings. For 105 days they lived underground until the arrival of the Soviet army in January 1945.
All of them survived, and immediately after the liberation were reunited with the rest of the Kostanskis. Wladislawa married Ajzyk in 1946, and soon after, Jan married Nacha. In 1957 Jan and his family moved to Melbourne, Australia. In April 1984 Jan and Wladislawa Kostanski were recognized by Yad Vashem as Righteous Among the Nations.