Kammala wannan jumlar: An haifi Fassbinder a cikin karamin garin Bad Wörishofen a ranar 31 ga Mayu 1945. An haife shi makonni uku bayan da sojojin Amurka suka mamaye garin da kuma
mika wuya ba tare da wani sharadi ba na Jamus. Sakamakon Yaƙin Duniya na II ya shafi rayuwarsa da rayuwar iyalinsa sosai. Dangane da burin mahaifiyarsa, Fassbinder daga baya ya yi iƙirarin cewa an haife shi a 1946, don tabbatar da kansa a matsayin ɗan lokacin bayan yaƙin; an bayyana shekarunsa na gaskiya jim kaɗan kafin mutuwarsa. Shi ne kawai yaro na Liselotte Pempeit (1922 <unk> 93), mai fassara, da Helmut Fassbinder, likita wanda ke aiki daga gidan ma'auratan a Sendlinger Straße, kusa da gundumar jan haske ta Munich. Sa'ad da yake ɗan wata uku, iyayensa suka bar shi da kawunsa da gwaggonsa a ƙauye, domin suna tsoron cewa ba zai tsira ba a lokacin sanyi. Yana ɗan shekara ɗaya sa'ad da aka mayar da shi wurin iyayensa a Munich. Mahaifiyar Fassbinder ta fito ne daga Free City of Danzig (yanzu Gdańsk, Poland), daga inda Jamusawa da yawa suka gudu bayan Yaƙin Duniya na II. A sakamakon haka, wasu cikin danginta suka zo su zauna da su a Munich.