Lovely illustrations here.
http://realcrusadeshistory.blogspot.com/2020/01/
From the beginning of the 14th century, the Ibelins claimed their descent from the Counts of Chartres, but most historians dismiss this claim as concocted. Peter Edbury, one of the most important modern historians of the crusader states, writing in 1991 claims "onomastic evidence points to a presumably less exalted Italian background, perhaps in Pisa or Sardinia.” (Edbury, The Kingdom of Cyprus and the Crusades 1191 -1374, p. 39) Six years later, however, Edbury had revised his thesis slightly, now suggesting Tuscan or Ligurian origins (Edbury, John of Ibelin and the Kingdom of Jerusalem, p. 4).
Sir Steven Runciman, in contrast, claimed that the house of Ibelin “was founded by the younger brother of a certain Guelin, who was deputy viscount of Chartres, that is to say, the Count of Blois’ representative in Chartres; and such officers in those days did not enjoy hereditary rank but were often drawn from lawyers’ families.” Runciman's preference for this version may have been influenced by the hindsight: so many of the 13th-century Ibelins were renowned lawyers.
Whatever his place of origin and whatever he called himself before coming to the Holy Land, the first man to identify himself as an “Ibelin” was a certain Barisan. Not only are his origins unknown, so is his date of birth. All that we know about him for certain is that in 1115 he was already “Constable” of Jaffa. To hold such an important and vital post, he would have had to be a fairly mature man, one who had already proved himself, especially in light of his non-noble birth. A date of birth around 1185 is therefore most logical.