Complex sentence: According to legend Cassandra, having been given the power of prophecy by Apollo, taught it to her brother; like Cassandra he was always right, but unlike her others believed him, making him more useful.
Split into simpler sentences: According to legend, Cassandra, having been given the power of prophecy by Apollo, taught it to her brother. Like Cassandra, he was always right, but unlike her, others believed him, making him more useful.