He was a member of a Hungarian-Croatian noble family of Jewish origin, founded by his paternal grandfather, John I Ernuszt.
Caspar was the youngest son of John II Ernuszt, Ban of Croatia, Dalmatia and Slavonia and his third wife, Barbara Ország.
Nevertheless, Ottoman numerical superiority was decisive and Croats were forced to retreat more and more to the west and northwest.
He himself helped people by setting ferries on the Drava and Mura river which enabled the refugees to cross them and go further north to reach western Hungary, which was still not occupied.
[1] After Caspar's death, his father-in-law Petar Keglević assumed ownership of his possessions in Međimurje.