Lion Mendels was a son of Jacob Levie Mendels and Cato Gomperts. He married 16 December 1902 in Amsterdam Pauline Rudelsheim, a daughter of Soesman Rudelsheim and Marianne van Weerden. The couple had two daughters, Germaine Madeleine and Cecile Marcelle. The marriage however ended by divorce on 8 September 1930 and Lion remarried 5 November 1930 the ladies fashion hat maker Heintje van Schaak.

Lion was born into a family of eight children, of who he self, his brother Adolf and his sister Charlotte have been killed during the Holocaust.

City Archive of Amsterdm, archive card of Pauline Rudelsheim and website www.wiewaswie.nl.