Complex sentence: He had two half-brothers, Ptolemy Keraunos and Meleager who both became kings of Macedonia (in 281 BC and 279 BC respectively), and both died in the Gallic invasion of 280-279 BC (see Brennus).
Split into simpler sentences: He had two half-brothers, Ptolemy Keraunos and Meleager, both of whom became kings of Macedonia (in 281 BC and 279 BC respectively). Both died in the Gallic invasion of 280-279 BC (see Brennus).