Their son, Kurt, was able to emigrate to Uruguay by the end of 1938 he arrived there on January 30th 1939. There is a file at the Hauptstaatsarchiv in Düssledorf about his emigration with letters from his parents.
In Hamburg there are 2 Stolpersteine dedicated to Ernst and Mathilde Lychenheim.
Please contact me, if I can be of any help.
Addition
Kurt Lychenheim
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