Complex sentence: He was the son of Valdemar II of Denmark by his wife, Princess Berengária of Portugal, and brother to Abel and Eric IV. He was elected King upon the death of his older brother Abel in the summer of 1252.
Split into simpler sentences: He was the son of Valdemar II of Denmark by his wife, Princess Berengária of Portugal. Christopher was elected King upon the death of his older brother Abel in the summer of 1252.