Eli Posen was married to Meta Dorothea Prins. His wife attended the wedding of their son Jacob Posen. The wedding was performed at Westerbork transit camp on 29 September 1943. Meta Posen-Prins signed the marriage certificate.
Record of marriage certificates of the Westerbork municipality, currently at the archives of Gemeente Midden-Drenthe in Beilen
In addition, a Jokos file (number 51931) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.The Jokos file reveals that a claim was lodged for compensation for valuables surrendered to the Lippmann-Rosenthal looting bank (L-claim, number 9739/21337).