Complex sentence: The island served at the time as residence to John V Palaiologos, one of three co-emperors to the throne of the Byzantine Empire, the others being his father-in-law John VI Kantakouzenos and brother-in-law Matthew Kantakouzenos.
Split into simpler sentences: The island served at the time as residence to John V Palaiologos, one of three co-emperors to the throne of the Byzantine Empire. His co-emperors were his father-in-law John VI Kantakouzenos and brother-in-law Matthew Kantakouzenos.