Matthew 10.34: "Do not think that I have come to bring peace upon the earth. I have come to bring not peace but the sword." Jesus is the cause of division, as there is a chasm between those who follow him and those who do not. Only the unbeliever can eliminate that separation by turning himself to God.
Speaking of changing oneself, fundamental change must come from within the heart. We have no power to change anyone fundamentally except through God. To initiate the change, the person involved must again turn to God to ask for it himself.