He was born in Vienna, the son of Count György Festetics de Tolna, who served as Minister of Foreign Affairs of Hungary from 1867 to 1871, and his wife, Countess Eugénia Erdõdy de Monyorókerék et Monoszló (1826-1894).

[3] His paternal grandparents were Count Laszlo Festetics von Tolna (1785–1846) and his wife, Princess Josefine of Hohenzollern-Hechingen (1790-1856).

His maternal grandparents were Count Kajetan Erdődy (1795-1856) and his wife, Countess Ernestine of Lerchenfeld-Prennberg (1798-1863).

In 1880 Festetics married Lady Mary Victoria Douglas-Hamilton (11 December 1850, Hamilton Palace – 14 May 1922, Budapest), former wife of Albert I, Prince of Monaco.

[4] The couple had four children: On 21 June 1911 Count Tasziló Festetics de Tolna was made a Prince with the style of Serene Highness (Durchlaucht) by Emperor Francis Joseph I of Austria.