Having been the last male descendant of the Slunj branch of the Frankopan family, he was called "the Sword and Shield of the Remnants of Illyria" (Latin: "ensis et scutum Illyrici reliquiarum", Croatian: "mač i štit ostataka Ilirije").

His father is known for organizing and hosting the assembly of the Croatian Parliament in the Cetin Castle by the end of 1526, where Ferdinand I of Habsburg, the Archduke of Austria, was elected King of Croatia.

Several months before Ferdinand's election, Matija (English: Matthew) II Frankopan Slunjski, his father's brother, was killed in the Battle of Mohács in southern Hungary.

[6] In 1553 he asked Ivan Lenković, the captain of Senj, to send soldiers as reinforcement to the castles of Hrastovica and Cetin, and in 1555 he demanded that his serfs should not be obliged to work on fortifications at the border, but without success.

In 1565 he participated in the failed defense of Krupa Castle, where he had unsuccessfully begged Count Herbert von Auersperg, the imperial commander-in-chief, to send the army to attack the invaders.

Subsequently, Croatian forces, led by him and accompanied by his relatives Nikola VIII Frankopan Tržački and Juraj IV Zrinski, crossed the Una River near Kostajnica in September and broke into the temporary Ottoman occupied territory.

At that time he had only around 20 serfs left, so, since he fought almost permanently, the Croatian Parliament asked King Rudolf to give him some more estates which would enable him to get more revenues, but without result.

[8] He was on the way to his wedding in Moravia with his fiancée Judit, the daughter of László Kerecsényi,[9] retired captain of Szigetvár, one of the richest feudal lords in Hungary.

The death of the ruling Viceroy of Croatia, called "the Sword and Shield of the Remnants of Illyria" (Latin: "ensis et scutum Illyrici reliquiarum"), caused a great repercussion throughout the country, as he was the last male descendant of his family branch.