If your brother sins against you, go and tell him his fault between you and him alone Matthew 18:15
“Reckon him no more amongst the number of thy brethren. But yet neither is his salvation on that account to be neglected. For the very heathen, that is, the Gentiles and Pagans, we do not reckon among the number of brethren; but yet are we ever seeking their salvation” – St. Augustine