relationship

Relationship with one's sister who wishes to marry a non-Muslim

Q: My oldest sister is planning to marry a non-Muslim guy in a church in front of a priest. She is aware that she is going against Islam and says she is following her heart and mind. If this makes her a disbeliever, what is my relationship with my sister after she commences with this marriage? My parents are not in favour and have no say in this, what according to Islam are we supposed to do?

Relationship with one's brother who has left home to marry someone he wishes

Q: My youngest brother (on many occasions in the past) disobeyed and disrespected my parents because of a girl he wishes to marry. It has gone to the extent that he has packed up his things and left home. He is now planning to marry this girl. We have been told to just let him be. In the process my parents have became very ill and decided to leave their residential home to not be present when the wedding takes place. After he marries this girl, what is our role (according to Islam) in terms of our relationship with him and his wife?