Efroim Sack was married to Racla Rozen. He was a baker by trade. Their third child, a son named Israel David, was born in Westerbork transit camp on 29 May 1943.
Record of birth certificates of the Westerbork municipality, currently at the archives of Gemeente Midden-Drenthe in Beilen
In addition, a Jokos file (number 25099) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.