Mietje Coster was the youngest of the four children of Barend Coster and Betje van Coevorden. She was born in Rotterdam on 22 August 1918 and lived with her parents and unmarried brother Jacob at home in the Vlaggemanstraat 26a, where they came to live up from Februray 1936. Her sister Sara was already married in 1928 and lived elsewhere with her family, just as her sister Hendeline, who was married in 1933.
On 27 March 1940 Mietje Coster married Abraham Mug, who was born in Rotterdam as son of the deaf and dumb couple Isaäc Mug and Esther Brilleman. Since 1936 he lived with his family at Anna Paulownastraat 43a, but on 4 July 1939 he moved in with his future in-laws, the Barend Coster family, who lived already since 1936 at Vlaggemanstraat 26b. To provide for his family, Abraham Mug was active as a street-market vendor.
At some point, Mietje and Abraham moved to Doezastraat 29a, where her husband was arrested on 13 March 1942 because of black-trade. He remained in custody for the Sicherheits Polizei and was sent to Camp Amersfoort (Police transit camp Amersfoort) on 1 May 1942. From there her husband was put on transport “direction Auschwitz” on 16 July 1942, and was put to work there but in the end he lost his life there on 30 September 1942.
When Mietje was taken and carried off to Westerbork, somewhere in the summer of 1942, she was already pregnant for 6 or 7 months. In Westerbork she was granted a reprieve of deportation to give birth to her child and on 13 October 1942 her daughter Betsy was born in the camp hospital. Notes on her Jewish Council registration card show, that Mietje and her little baby-daughter were still in the camp hospital on 13 November 1942, in order to recuperate.
When Betsy was 5 months old and mother and daughter were found "strong enough", were both as recovered deported to Sobibor on 30 March 1943, together with more than 1250 other deportees. Upon arrival there on 2 April 1943, Mietje Mug-Coster, her 5-months old daughter Betsy Mug and everyone else were murdered directly in the gas chambers. There were no survivors.
Sources include the City Archive of Rotterdam, family registration cards of Abraham Mug, Isaäc Mug and Barend Coster; the file cabinet of the Jewish Council, registration cards of Abraham Mug, Mietje Mug-Coster and Betsy Mug; the Wikipedia website Jodentransporten vanuit Nederland.nl and additions of visitors of the website.