According to Allah and Muhammad, you don't have any Christian brothers and sisters. Qur'an (5:51) - "O you who believe! do not take the Jews and the Christians for friends; they are friends of each other; and whoever amongst you takes them for a friend, then surely he is one of them; surely Allah does not guide the unjust people."
Perhaps you can explain why that should lead to war, hate or even a mild argument. I, myself, can't think of any reasons.