As one of the wealthiest and most distinguished aristocrats in the kingdom in his day, he had one of the leading roles in mounting defences of Croatian statehood against the Ottoman expansion.

Although exposed to Ottoman sudden raids from Bosnia in the second half of the 15th century, Modruš stayed the seat of the family branch and of young Bernardin as well.

Among them there were Krsto (Christopher) – the future well-known military leader, Beatrica – the wife of Ivaniš Korvin, Ban of Croatia, Ferdinand, Matija, Ivan X Franjo, Marija Magdalena, Elizabeta, Eufrozina (Fruzsina) married Dessewffy Ferenc, and Katarina.

The life of Bernardin Frankopan was since his childhood marked by permanent tensions, conflicts and heavy battles, from which he tried to get benefit for himself, for his family and for Croatia.

As a young boy he sometimes accompanied his father during diplomatic missions and journeys (appointed by the Croato-Hungarian King Matija Korvin) throughout Europe and got acquainted with many notable and important people.

He spent some time in the court of the Friedrich III of Habsburg, Emperor of the Holy Roman Empire, in Graz, Austria, when he was a teenager (about 1469).

Because of bad military tactics ordered by the Croatian supreme commander Mirko (Emerik) Derenčin, Ban (viceroy) of Croatia, the aggressive Ottoman army won the battle.

Bernardin's sole heir remained his grandson Stjepan IV Frankopan of Ozalj, Ferdinand's son, who was still a boy when his father died.