John of Ibelin, (1215-1266). Lord of Beirut and constable of Jerusalem. He is the son of Maria Komnene (Matia Taronitiss, a descendent from the Armenian Kings of Taron) Queen of Jerusalem (1154-1217). 
He was married to Maria of Armenia (sister of King Hethum I of Armenia)
A noted jurist and and the author of the longest legal treatise from the Kingdom of Jerusalem.