Inschrijving Siegmund Ferdinand Sonnenberg in het Militieregister Amsterdam (Stadsarchief Amsterdam)
Bron: https://archief.amsterdam/indexen/persons?f=%7B%22search_i_datum%22:%7B%22v%22:%5B%2218700000%22,%2219479999%22%5D,%22d%22:%221870%20-%201947%22%7D%7D&ss=%7B%22q%22:%22Siegmund%20sonnenberg%22%7D&rows=250
Bertha Elisabeth Sonnenberg was a daughter of Adolph Sonnenberg from Hamburg (1855) and Carolina Wolff from Steenwijkerwold (1864). This couple married in Haarlem on 15 August 1894 and had five children in total, of whom a stillborn son in 1895 in Rotterdam.
A sister of Bertha was Helena Dorothea, b…