Isaäc Plas was a son of Jacob Plas and Judith van Kam. He married for the first time in 1912 to a woman who survived the war. From this marriage he had a son Jacob. The marriage was dissolved in 1932. He remarried on 22 April 1942 in Amsterdam to Margaretha Schelvis.
Stadsarchief Amsterdam, archiefkaart Isaäc Plas
In addition, a Jokos file (number 20777) on this person is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.