In my WIP, the half-brother of the MC and the MC's maternal uncle plot to take the kingdom away from the MC's family. The half-brother is the result of the MC's father and the father's first wife (who was his childhood friend he fell in love with.) They had a life together until the father's royal calling forced him to take another bride to solidify an alliance (In the world I'm writing polygamy is common practice). The new woman by default of her royal heritage became the primary wife (I.E. the one with all the political power). They had a son together (MC's older brother) who automatically became the heir, passing over the son the King had with his childhood romance. Obviously the first woman is pissed at losing her position so she tries to kill the boy. It fails and she and her son are banished. When the story starts, the half-brother has grown older and is convinced he should be King. The MC is sent to nip the problem in the bud before civil war breaks out. But since the MC is the youngest son, I'm not sure how much of the back-story he should have previous knowledge to. Should he know that he's being ordered to kill his own half-brother? Would that add much? What reasons would his father and his mother have for not telling him about what had transpired before hand? Any thoughts? Thanks in advance.