Does a male heir bear the sins of his divorced sister, and what are a son's responsibilities toward his mother and sister?

Summary

Every person who has reached puberty and is of sound mind bears his or her own sins, not parents, siblings or a husband. Parents or guardians are considered at fault if they let their children sin without advising or preventing wrongdoing. All family members are encouraged to advise one another, including knowledgeable siblings, with patience and a good approach.

Written in our own words from the original fatwa — check the source before acting on it.