Questions

I have questions.
Are we are brothers keeper?
Are we responsible for their behavior?
Do have an obligation to tell a christian brother if he has committed a sin?
Should we just pray that God convicts them of their sin?
Did God send us to be the messenger for him to confront their sin?
Should I just worry about my relationship with Jesus and not theirs?
Is there no blanket answer for all people?
Is there a different solution for different situations?