Complex sentence: Joanna was born at Naples, a daughter of Ferdinand I and his second wife, Joanna of Aragon, which made her a half-sister of Alfonso II of Naples and Frederick IV of Naples.
Split into simpler sentences: Joanna was born at Naples, a daughter of Ferdinand I and his second wife, Joanna of Aragon. She was a paternal half-sister of (among others) Alfonso II of Naples and Frederick IV of Naples.