Old letters found

Whilst clearing out my uncle's flat in Portsmouth (he is now in London in a residential home), I found a collection of letters dating from 1939-1940 addressed to him and to my mother from "Aunt Li" living at Leuvenschestraat 26, (NB not 33) Scheveningen. I don't know whether Aunt Li and her family were relatives or just friends of my family. The letters mention Onkel Max (who always seemed to be travelling to the USA) and their 2 sons "Bob" and "Frits". My late mother (Hanna Koebner, née Klein) and uncle (Julius, now aged 90) came to Britain from Düsseldorf on the Kindertransport. Their parents (my maternal grandparents) were Rabbi Siegfried and Lilli Klein. They were deported to Łodz Ghetto on 27 October 1941 and did not survive the Holocaust. Aunt Li evidently acted as postal intermediary between Siegfried and Lilli when the outbreak of war rendered correspondence between Britain and Germany impossible. The correspondence stops (or, alternatively, has been lost) after February 1940. I have relatively little information and documents about my mother's side of the family and was thrilled to find this correspondence, heart-breaking as it is. I would be so happy to find out more and wonder if any of the family is still alive. I live in London. My email address is: marionkoebner@gmail.com