On page 419 of Holy Blood, Holy Grail Lincoln et al state:
'And from Godfrey there issued a dynasty and 'royal tradition' which, by virtue of being founded on the 'rock of Sion' was equal to those presiding over France, England and Germany. If the Merovingians were descended from Jesus ... then Godfrey ....in his conquest of Jerusalem, regained his rightful heritage'.
They had referred to the opus by Rene Grousset, 'The Epic of the Crusades' and the Godfrey in question was the famous Godfrey de Bouillon.
On page 279 the authors had concluded '...what can one do if one is a king without a kingdom? Perhaps find a kingdom, or create one. The most precious kingdom in the entire world was Palestine, the Holy Land, the soil trodden by Jesus himself...'
The suggestion here of a Monarchy being founded on the Rock of Sion was first promulgated by Rene Grousset, respected historian of the Crusades. However, what Grousset had in mind, when talking of this Jerusalem Monarchy was not one created from any descendant of Jesus Christ - but one which was a military monarchy created by Baldwin of Boulogne, brother of Godfrey, and NOT Godfrey, as Lincoln et al wished to convey in their book, Godfrey de Bouillon.
It was Baldwin, Grousset said, that built a kingdom based on the Rock of Sion, where the 'Rock of Sion' was based on the divine Monarchy of King David and Solomon. This was pretty much what all the reigning dynasties of Europe also promulgated - a divine Monarchy with a divine right to rule from Old Testament Kingship/Royalty. Lincoln et al therefore manipulated the original idea of Grousset into one singular idea - that Godfrey de Bouillon, as a direct descendant of the historical Christ, was reclaiming the right to rule as king in his antecedents stead.
'Baldwin of Boulogne, the first Frankish King of liberated Jerusalem, was therefore certainly not a saint, as was his brother Godfrey of Bouillon: but from the political point of view, he had undoubtedly been the man of the hour, cut to the measure of the epic, or rather dominating it, since he alone among all these paladins fully understood how to make this epic a reality, to his own advantage. In him the unscrupulous adventurer had quite naturally and quite continuously given place to the statesman. Violence and patience, fire and caution, hypocrisy or cynicism, loyalty, brutality, or perfidy, crimes as well as virtues - but crimes committed for public safety, virtues of a chief - all these elements in a closely woven personality were controlled and dominated in him by reasons of state, ordered with an eye to reasons of state. The ancient Greeks, in the manner of empire builders, would have surnamed him Baldwin the Founder ......this Frankish state of Jerusalem, born of surprise, was to find itself, once established by him, so firmly founded by him overnight that no one after him ventured to challenge it. .... he made this borderland of Christendom what it must be if it was to remain viable - a solid military monarchy. The patriarchate, in the hands of his friend Arnulf Malecorne, became the faithful partner of this policy.... it must not be forgotten that before girding his sword, Baldwin had been a son of the Church, a former canon of Cambrai and intellectually the ordered Roman mind. He created majesty. He even created a legitimacy by divine law, and the most sacred in the Christian world ..... by linking himself with the royalty of David and Solomon.....in the eighteen years of his reign he even succeeded in laying the foundations of a monarchical tradition much superior to other Monarchies .... because being founded on the rock of Sion, was equal or superior to that of the Capetian kings of France, the Norman kings of England, or the Germanic Roman Emperor.
The whole subsequent history of the kingdom of Jerusalem remains his work.' (Grousset, The Epic of the Crusades, 1970, page 74).
This military monarchy of Baldwin was to be 'kept in the family'. In these origins I also see the rise of the Knights Templar, perhaps suggesting that this military army was associated with the same military Monarchy envisioned by the family of Godfrey de Bouillon. Godfrey had died unexpectedly on 18 July 1100. He had extracted oaths from Daimbert and other leading crusaders that they "would not confer the throne on anyone except his brothers or one of his blood", according to Albert of Aix. Warner of Grez, Godfrey's most influential retainer, took possession of the Tower of David in Jerusalem to secure control of the city. Although Warner soon died, two other members of Godfrey's court, Geldemar Carpenel and Arnulf of Chocques, sent a delegation to Baldwin, urging him to come to Jerusalem.
Here then Grousset says that the Jerusalem Monarchy was created when Baldwin linked himself to King David and King Solomon - and to Old Testament kingship generally. David and Solomon were Kings of Israel and of Jerusalem. Because Baldwin became a King in this manner it was equal to the royal tradition of David and Solomon as kings of Sion (Jerusalem). This 'new' Kingship could be seen as equal to all the other reigning dynasties of Europe precisely because they all aspired to the concept of Old Testament kingship. Baldwin was equal to other kings, or even superior, because he created the Kingdom of Jerusalem, where the divine right to rule first appeared with David and Solomon. I see no evidence that Baldwin created the Kingdom because he was a descendant of Jesus. Lincoln et al surely knew this when they used the Grousset quote?
There was also another subtle difference. King David and Solomon received their right to rule direct from God. Baldwin, however, had heeded the call of the Church and its Pope to rescue Christendom and Jerusalem from the 'infidels'. Was he then able to rule in the 'royal tradition' of David and Solomon, or because of the Church and its Pope and its authority?
You can read more about Baldwin and his kingdom HERE.