Eugen Dido Kvaternik was the son of Slavko Kvaternik, a general in the Independent State of Croatia army and a member of the Ustaše, and Olga Frank, daughter of Josip Frank, a Catholic convert whose parents were Jewish.

Kvaternik was sentenced to death in absentia by France for organizing the assassination of King Alexander I of Yugoslavia.

However, at the time, he was imprisoned by authorities in Fascist Italy, who refused to hand him over for execution.

He was released in 1936, having served two years, whereupon he joined the exiled Ustasha members on the island of Lipari.

Slavko later became a professor of political sciences in Argentina, and Davor became a cardiologist in Boston, Massachusetts.