Before proceeding with any solutions, the examination of documents is required, so as to know the actual truth as per law. Here are some pointers which are required to be looked upon, only then can we come to a conclusion.
1. Reports regarding citizenship proof.
2. Marriage certificate.
3. Terms and conditions for getting involved in this marriage.
4. Time spent by her with your brother in UK.
5. Place of marriage.
6. Mode of marriage.
7. Religion of both the parties.
8. Proof of the disease faced by your brother.
9. Proof that the girl was aware of the disease and the terms and conditions you have stated above prior to marriage.
If all the things are positive and in favour of your case, then in that case a writ-petition can be filed in high court for getting a positive direction in favour of you brother as well as his parents/relatives.