In my opinion, i think it is helpful to confront a brother alone first because, he is your brother and you will be able to talk to him honestly with an open heart and with love and respect showing him or her how much they've hurt you. They will listen to you, sometimes they may not say anything at that moment, but with time, they will know that they are really wrong and needs to say sorry or at least, let you know why they did what they did.

If after a while they did not say anything. talk to them again alone and if no show of remose or sorry from them, than you can involve others to confront them in your presence, so no misunderstanding of talks.

Those who do not know Jesus are like lost sheep because they are living life without purpose,  hope, future and the ultimate goal of eternal salvation.

They are lost because they do not know the way or dont want to follow the way that will lead them to eternal life.