Alexander Mogendorff was a son of Michael Mogendorff and Sara Frankfort.
This couple married in 1926 in Amsterdam.
Addition of a visitor of the website
It is not clear where Alexander Mogendorff died. The War Graves Foundation says that he died in Amersfoort concentration camp (Leusden) and that he was cremated in Velsen. In 1948 the urn with his ashes was placed in the Jewish cemetery in Muiderberg. A list (at NIOD) of Westerbork and Buchenwald concentration camps mentions that Alexander Mogendorff died in Buchenwald.
A third source, a monument at the Jewish cemetery in Muiderberg, mentions Mauthausen as the place of death. Alexander Mogendorff could have belonged to the group of 400 men who were arrested during the first raid in Amsterdam.
Addition of a visitor of the website