German physician, psychotherapist, and author, the eldest son of artist Käthe Kollwitz; in his retirement he published her writings and a monograph of her sculptures.
Hans Kollwitz was the first son of the physician John Carl August Kollwitz and his wife, Käthe. As children, Hans and his younger brother Peter were frequent artist models for their mother. Hans was depicted as a baby and a small child. From 1904, he and his brother grew up together with Georg Gretor, Käthe Kollwitz’s “foster son” from Paris, the son of her student friend Rosa Pfäffinger and her husband Willy Gretor.
As a youngster, Hans Kollwitz was a member of the Wandervogel, a left-wing bourgeois youth movement, along with Walter Benjamin, Hans Blüher, Ernst Joëll, Fritz Klatt, the brothers Hans and Walter Koch, Erich Krems, Alfred Kurella and Alexander Rüstow.
From 1908, the 16-year-old Kollwitz was involved in a student newspaper project, which later became known throughout the empire. First published in 1911, the youth magazine Der Anfang (The Beginning) featured Kollwitz’s writing and brother Peter’s drawings; two cousins ??also contributed drawings, and Georg Gretor wrote articles. Georg Gretor published under a pseudonym as Georges Barbizon, after his hometown Barbizon near Paris. Other authors included Walter Benjamin and Siegfried Bernfeld, while Gustav Wyneken was editor. In Bavaria Der Anfang was banned in all schools.
Kollwitz began studying medicine at the Friedrich Wilhelm University in Berlin around 1910. After the outbreak of the First World War, he volunteered and was recruited to the medical service. On 23 October 1914, only ten days after his departure to the Western Front, his younger brother Peter died, aged 18, during combat in Flanders.
In 1919 Hans Kollwitz married the graphic artist and book illustrator Ottilie (nee Ehlers, 1900-1963). The marriage produced four children, Peter (1921-1942), the twins Jordis and Jutta (born 29 May 1923) and Arne (born 1930). They named their first son after Hans’s deceased brother Peter.
After receiving his doctorate in 1920, Kollwitz joined the health administration of the Reich capital. In 1928 he became a school doctor and later epidemic officer for Berlin.
In 1942, his son Peter died at age 21 on the Eastern Front. In December 1943, the family property was severely damaged by an air raid, such that their house was no longer habitable.
After the death of his mother in 1945, he became first deputy medical officer in the health administration of Berlin-Tempelhof and devoted himself to his psychotherapy practice. He retired early and dedicated himself to the memory of his artist mother. He published a selection of her diary entries and letters, supported exhibitions of her work and published an illustrated book with photographs of her sculptures.
Hans Kollwitz died on 22 September 1971, aged 79, in Berlin. He was buried next to his wife; the bronze relief “Rest in the peace of his hands” by Käthe Kollwitz was integrated into the tombstone.

Link to Wikipedia biography (German)