Yup.. you confront him first one on one. Them you get two or 3 other brothers to show him according to scripture you are "living in sin". But if they still dont want to do it then you shake the spot. If they repent and get it right then you have gained a brother
Yea you are
Leveiticus 19:17
Thou shalt not hate thy brother in thine heart: thou shalt in any wise rebuke thy neighbour, and not suffer sin upon him.
Galatians 6:1
Brethren, if a man be overtaken in a fault, ye which are spiritual, restore such an one in the spirit of meekness; considering thyself, lest thou also be tempted.
Titus 3:10
A man that is an heretick after the first and second admonition reject;
Deuteronomy 19:15
One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sinneth: at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established.