Please advise

i) As advised go in for annulment of petition on the grounds of non consummation of marriage on the grounds of impotency.

ii) Offence of cheating (417 and not 420) is also attracted in the facts of the case, but you'd have to prove that your brother in law had the intention to decieve at the time of representation of potency (if any). But it would be very difficult to fasten criminal liability in absence of a specific fraudulent representation of potency.

I second the advice advamced by Bharat. However, if a complaint is filed as against the husband for cheating u/s 417 of I P C, only thing which will have to be established that the husband or any of his family members did not disclose the fact that the husband was impotent and hide the same to deceive the girl and her family members.

I feel it is "being non-committal about the problem of impotency" that attracts provisions of S.417 and S.420 of IPC rather than "fraudulent representation of potency" because no one generally makes any claims on potency during or prior to marriage, which claim in itself is very absurd to make.