Although Magnús' eldest brother, Haraldr Óláfsson, appears to have ruled over the entirety of the dynasty's thirteenth-century sea-realm, as did Magnús from 1252 onwards, the situation during the years between Haraldr Óláfsson's death and Magnús' accession is uncertain, and it is possible that the kingdom was partitioned between feuding dynasts, as it had been during the bitter inter-dynastic strife of the twelfth- and thirteenth centuries.
Although Magnús' eldest brother, Haraldr Óláfsson, seems to have controlled the entire dynasty's thirteenth-century oceanic realm, as did Magnús from 1252 onwards, the situation during the years between Haraldr Óláfsson's demise and Magnús' ascension is unclear, and it is possible that the kingdom was divided among feuding rulers, as it had been during the intense inter-dynastic conflict of the twelfth- and thirteenth centuries.