In 1926, their son Horst Kaźmierczak was born. The family Germanized their family name from Kaźmierczak to Kasner in 1930. They still kept in contact with the Polish side of the family, visiting them in Poznan several times in the 1930s as well as receiving visits in Berlin by Polish relatives. Despite the name change, Ludwig Kasner's nephew Zygmunt Rychlicki said he always stayed true to his Polish roots.