does the brother have the right to abuse his sister when she does something wrong. and if she had sex before marriage does the brother or anyone from her family allowed to kill her . and what is her punishment ?

In the name of Allah, Most Gracious, Most Merciful

Assalaamu `alaykum waRahmatullahi Wabarakatuh

If a person commits a sin, then the family members are not allowed to physically harm the person in any way.  It is the role of the Muslim government, not the citizens, to establish punishments for sins, such as zinā.  In the lack of such a government, the family members should take other preventive measures, such as getting the woman married, to ensure such mistakes are not repeated.

And Allah knows best

Wassalaamu `alaykum

Ml. Abrar Mirza,
Student Darul Iftaa

Darul Iftaa