 According to the Chronicle of Mann Guðrøðr , in 1187 , instructed that his younger son Óláfr should succeed to the kingdom , since Óláfr had been born " in lawful wedlock " . Other contemporary sources record that two decades prior to this the papal legate , Vivian Cardinal priest of St Stephen in Celio Monte , visited Mann for a fortnight in late December 1176 , as he sailed from Scotland to Ireland . The chronicle records that during his visit the cardinal formally married Guðrøðr to Finnguala , daughter of an unnamed son of Muirchertach Mac Lochlainn , High King of Ireland ( d . 1166 ) . Finnguala 's father was more than likely Niall Mac Lochlainn , King of Cenél nEógain ( died 1176 ) . Since the chronicle contradicts itself in detailing Óláfr 's age , it is uncertain whether he was born during the year of his father 's marriage , or a few years before — what is certain , however , is that Rögnvaldr was older than Óláfr . 
