Jacob and Rosetta Nihom lived with their parents behind their store in Nijkerk, Gelderland. In 1941, they were contacted by Mr. Henk Sietsma who offered to be the children's guardian. At this point the strictures on Jews were not threatening enough for their parents to agree to this. In January 1942, a Jewish high school was established in Utrecht, and the two teenagers used to travel 45 kilometers every day to attend, but when Jacob received an order to report to a work camp in Holland, the family decided that the time had come to go into hiding.
The Sietsma brothers, who had formed the Group Hein, an underground resistance group which assisted Jews in going into hiding, were instrumental in providing places for the family to hide, obtaining food stamps and issuing false ID papers. Other members of this group were Mr. Harry Aldenzee, Jan and Dinie van Meerveld as well as Ab and Hendrika van Meerveld-van 't Hof, Aalt and Ali Lozeman and Piet Hartog.
Hein Sietsma (1919-1945) was arrested in Friesland on April 28, 1944, by the train controllers and deported to Dachau, where he died. Henk survived the war, after incarceration in a concentration camp in Germany. Henk estimates that nine families and eleven individuals at least were saved by the Group Hein. The group also saved the lives of many British and American air force men.
In April 1977, Yad Vashem recognized Hein and Henk Sietsma as Righteous among the Nations.