Complex sentence: In 1580, more than 40 years after her death, her son Philip succeeded the Portuguese throne, claiming his mother's successory rights temporarily uniting the Iberian peninsula under one crown in what would later be called the Iberian Union.
Split into simpler sentences: In 1580, more than 40 years after her death, her son Philip succeeded the Portuguese throne. It was he who claimed the successory rights to the throne of Portugal that temporarily united the Iberian peninsula under one crown in what would later be called the Iberian Union.