Complex sentence: He claimed the throne, apparently in tandem with his younger half brother Boleslas Sverkerson, after his half brother Charles Sverkersson when he was murdered by Canute Ericson, and held the throne in opposition to Canute for a few years.
Split into simpler sentences: He claimed the throne, apparently in tandem with his younger half brother Boleslas Sverkerson, after his half brother Charles Sverkersson was murdered by Canute Ericson. He held the throne in opposition to Canute for a few years.