Valentine and Ender's older brother, Peter is completely lacking in the compassion that the other two have and has only ruthlessness in its place. He is a sadistic brother and it is unclear at many points whether or not he is considering killing Ender and Valentine. Peter is the mastermind behind the actions that he and Valentine take in world political affairs, and he is motivated by his thirst for power. His lack of compassion makes Peter a man devoid of humanity. He acts solely for his own benefit and, although he has a profound understanding of others, uses his knowledge only to probe their weaknesses to his own advantage.
Peter eventually gains power over the entire earth and becomes the Hegemon, the leader of the world. He is able to do so peacefully, although this is not necessary for him, it was merely the most expedient way to gain power. The difference between Peter and Ender, although it sometimes seems slight, is in reality a fundamental difference. Other people matter too much for Ender to do willingly endanger them, but Peter takes the opposite path. He is concerned only with himself, and although this leads him to be the ruler of all humans on earth, it makes Peter as far from human as possible. It is the nature of power, and the effect it has on people, that creates the resemblance between Peter and Ender.