Matthew 18:16 (CSB) "But if he won't listen, take one or two others with you, so that by the testimony of two or three witnesses every fact may be established.
If the one who has sinned against us does not repent at our rebuke, then we are to take a few others with us. These ought to be people who are more mature in The Lord and who is respected by the other person. If we brought people who is disliked by the one who sinned against us then they still won't listen to us. These two or three others need to agree with you that the brother or sister has indeed sinned against us. They would have either saw it or have heard both sides of the story and agree with our side. Galatians 5:24-6:1 (CSB) 24 Now those who belong to Christ Jesus have crucified the flesh with its passions and desires. 25 If we live by the Spirit, let us also keep in step with the Spirit. 26 Let us not become conceited, provoking one another, envying one another.6:1 Brothers and sisters, if someone is overtaken in any wrongdoing, you who are spiritual, restore such a person with a gentle spirit, watching out for yourselves so that you also won't be tempted. 1 Corint