Complex sentence: Because of what he viewed as the inaction of the various rival monarchs de Fortis promoted a new king in Cedric Boston (born on Montserrat in 1960), who claimed the Redondan throne in 1984 and won the allgiance of a number of Gawsworth's peers.
Split into simpler sentences: Because of what he viewed as the inaction of the various rival monarchs de Fortis promoted a new king in Cedric Boston (born on Montserrat in 1960). Boston claimed the Redondan throne in 1984, winning the allgiance of a number of Gawsworth's peers.