Early in his high school days , he joined the Pure Party of Rights as well as the Frankovci students ' organization , founded by Josip Frank , father-in-law of Slavko Kvaternik , an Austro-Hungarian colonel .
An extremist even in his youth , he became a member of the organization known as the `` Frankovci '' whose founder , Dr. Josip Frank , was the father-in-law of Slavko Kvaternik , an Austro-Hungarian army officer .