Ilse is one of four victims of Auschwitz concentration camp who are commemorated on Oskar's gravestone. She was living at the same address as Oskar and several relatives at the time of the 1939 census which names her as Ilse Bielschowsky geb. Apt, and I suggest she was his daughter.

Yad Vashem records give her married name as Bielschowsky; I assume she is the mother of the two children listed at the same address with the surname Apt-Bielschowsky.

Ilse and Peter were deported from Berlin to Auschwitz concentration camp on 17.05.1943.