Following his parents' assassination, which precipitated World War I, Ernst and his siblings, Sophie and Maximilian, were taken in by their uncle, Prince Jaroslav von Thun und Hohenstein.

In late 1918, their properties in Czechoslovakia, including Konopiště and Chlumec nad Cidlinou, were confiscated.

Prince Ernst, having previously spoken at pro-monarchist meetings and having publicly opposed the Anschluss, was sent to Dachau concentration camp with his brother.

She was daughter of Captain George Jervis Wood (1887-1974) and his wife, Countess Rosa Lónyay de Nagy-Lónya et Vásáros-Namény (1888-1970), daughter of Count Albert Lónyay de Nagy-Lónya et Vásáros-Namény (1850-1923) and Princess Marie of Hohenlohe-Bartenstein (1861-1933), elder sister of Princess Eleonora Fugger von Babenhausen.

The couple had two children: Prince Ernst died at Graz in Austria in 1954, aged 49, his death considered to be connected to mistreatment he suffered in the concentration camps.