Complex sentence: Sourmush had killed a member of a rival clan while drunk; to prevent the outbreak of clan warfare for blood revenge, the clans decided either Charles Hughes or his nephew James Vann had to die to assuage Sourmush's crime.
Split into simpler sentences: Sourmush had killed a member of a rival clan while drunk. To prevent the outbreak of clan warfare for blood revenge, the clans decided that either Charles Hughes or his nephew James Vann should die to assuage Sourmush's crime.