Turning from the historical to the fictional characters in the Last Crusader Kingdom, I want to start with Lakis the Orphan. Lakis is the second character introduced in the novel, making his first appearance in the Prologue.
Lakis' function in the novel is two-fold. He represents on one hand a youth of the working class and on the other the Greek victims of the insurgency.
When John first encounters Lakis, John has disguised himself as a servant. This enables him to mingle with people he would not otherwise meet. Because a servant is less intimidating to the beggared Lakis, John is able to win a decree of trust. Through Lakis, John has a glimpse of the lives of working people.
More important, however, Lakis is a victim of the ongoing civil war on Cyprus. His parents, home and future-livelihood have been destroyed in a reprisal raid by Guy de Lusignan's men. Significantly, the raid was led by John's cousin Henri de Brie, which gives John a sense of guilt for what happened. This, in turn, makes him ask more questions and look for solutions as he might otherwise not have done. In short, Lakis gives the Greek Orthodox population a face. The abstract wrongs Aimery and others bemoan are suddenly more real for John -- and the reader.
Lakis also serves as the bridge between the two worlds as well. Through him, Balian is able to make contact with the leader of the rebels. Yet, Lakis continues to inhabit a different world from John. Once John's true identity is revealed, there can be no more friendship, only patronage. Thus John's relationship with Lakis is a measure of his level of responsibility and so his progress on the road to his destiny as a leading baron in two kingdoms.