Marriage to a married woman in order to get citizenship

My question is in regard to marriage. My wife is married by paper to my brother so that he can get his citizenship. I am married to her Islamically. She is often worried that this is Haram and we have many discussions on this topic. We need a more clarifying answer to put this issue to rest, she is very worried.

Praise be to Allaah. 

If your marriage was contracted first and was done according to the conditions of sharee’ah, then she is your wife, and your brother’s marriage to her is invalid and does not count. He has to repent to Allaah from what he has done, and you and your wife also have to repent to Allaah if you helped him to do that. Let your wife rest assured that your marriage to her is valid so long as all the conditions required in sharee’ah were fulfilled. And Allaah is the guide to the Straight Path.