“If your brother sins against you, go to him and show him his fault. But do it privately, just between yourselves. If he listens to you, you have won your brother back.
Here is the clear difference between God's children and the Devil's children: those who do not do what is right or do not love others are not God's children.
We must not be like Cain; he belonged to the Evil One and murdered his own brother Abel. Why did Cain murder him? Because the things he himself did were wrong, and the things his brother did were right.