About Unknown Rushanski
There is a third child noted in the testimony of Chana Shlang, sister of Efraim Rushanski, no name, age 3.
Chana Schlang gave two different testimonies as to the location of the death of her brother and his family. I am assuming that the one that is more specific (Auschwitz) is correct. The other one says they died where they lived in Druskieniki.