István Fáy was born 7 July 1925 in Budapest, Hungary to Móricz Fáy (1880-1935) and Adél Hänisch (1893-c1970) .
Siblings
| Name | Birth | Death | Joined with |
| Valéria Fáy (1920-1977) | 20 December 1920 Nagytétény, Pest County, Central Hungary Region, Hungary | 17 March 1977 Budapest, Hungary | Antal Béla Schubert (1921-1972) |
| Klára Fáy (1923) | 14 March 1923 Miskolc, Borsod-Abaúj-Zemplén County, Northern Hungary Region, Hungary | ||
| István Fáy (1925) | 7 July 1925 Budapest, Hungary | ||