 Complete the following phrase:  In the 1520s he lost two of his sons, Ferdid and Krsto Christopher the latter falling during the siege of Varaždin castle on 27 September 1527. His daughter Beatrice died in 1510, while her three children from the marriage with John Corvinus died before her. Bernardins sole heir remained his grandson Stjepan IV Frankopan of Ozalj, Ferdids son, who was still a boy when his father died. Stjepans sister Katarina married Nikola Šubić Zrinski, future hero of 