Let me explain "a guy’s point of view" on your relationship. It seems to me that you are running behind a relationship, which your mister assume that is already dead. He is not able to get-in/get-out of the relationship because of some pressure, either socially, morally, legally, financially or some other aspect. I’d understanding that he was facing some challenges immediately after the marriage from either your progress or his fallback. Your relationship is into a one-sided ego issue which is why it’s taking time to get resolved. If your husband is around 25-26 years, give him some time to understand the life and have various experiences in his life. Your relationship is temporarily dead not actually dead. If you could drag this relationship for some more time, probably a year or so, he would start feeling something for you and chances are fair that you would get back into this relationship again. It’s kind of chance, you would be taking by giving him neutral response.
Don’t put something in the court which can disturb someone else’s life. You would NOT get any benefit out of it. At least, putting his sister name is NOT going to help in this case. Those emails could be proved as response to some other request. I don’t think so that anyone in this world will write in clear words that they need dowry when he/she knows that it’s a crime.
If you want to have a relationship with this person then you do NOT have to respond him in an aggressive manner. You have done very well so far and you really do not have to put any legal condition to settle down in this relationship. Would you be happy to have a husband who is bounded with you legally not morally? You know the proverb that "what goes around comes around". If you are going to take down his sister then he would probably bite back your sister/mother as well. Give him a feeling that you love him; Show him that "you as a wife" don’t have to prove anything legally. He already knows that you are going to win this battle in a long-run. It will be he, who will end-up paying alumni money, maintenance and other charges in the divorce case.
A person cannot remain angry for a long time if he/she does not have any reason for it. Pray and think positive all the time. Call him with love when you are in the mediation centre and try to show your love. You need him back into your life. You do NOT want to lose him and you do NOT have to lose him necessarily. Don’t just think that if he has filed a case on you then he is going to keep that false and baseless case going-on for a longtime.
Also, please don’t rush in taking divorce… You would be probably not aware about the after divorce life as well... Let me explain this aspect as well.
The moment you will have divorce papers in your hand, you would NEVER EVER want to get into any new relationship at all! You will always have this terminator-2 theme going on in your mind; What if your new husband called someday, a final judgment day! What this social world will call you then? With this feeling, you would not able to start a new relationship "immediately". As the time goes-by, says 6 months or so, you would start getting the pressure from your parents, friends, social elements or for biological needs. Your parent will knock-out every other possible matrimonial site to match your horoscope, gun-milap, stars and so called "panditji business". You would also realize that time is running out of your hand and the first guy, you would meet in this God’s divorced world will be chosen as husband. May be, you does NOT want to have a divorcee husband for various reason but chances are fair that with 60-40% feeling, you would jump into the wedding "water-well" to save your "left-over" world. Everyone is this damn world will suggest you to think positive and you can swim very well in this new "water-well". You would probably try to sync-up with their feeling and your emotions too. The moment you are into this new relationship, you would start comparing your new husband with old husband and that will go for some time. Your husband in-turn will do the same thing; your husband will have the scare feeling also that anytime, the divorce bell could ring again... He would keep thinking to shoot the alumni/maintenance animal down by registering the FIR first case in case of any fight... From the time, "I do" to "I argue".... It will change into the whole world... Even a small domestic fight will turn into a domestic violence case! My close friend is going through this wedding retake trauma again... I just want to let you know that don’t plan your future just based on some assumptions...
My "great" wife has NOT left any sections under marriage act to say that you are the most awesome wedded husband ever in the men’s criminal history! From husband to respondent, it was quite a journey for me. So based on my experience, I can say that you should not proceed in a “bad legal way” to make-up this relationship.
Think twice before you take any decision... Have patience, you will win this case from both the ends... God Bless You!