@ author
Very sorry to hear your story.
If they have married without you getting divorce,you can punish them both under an IPC section about which only a lawyer can tell you.
If they are having a live-in without a marriage,I am sorry they cannot be convicted.This is the beauty of Indian judiciary.On one hand it talks about giving "rights" to legally wedded wives.On the other,it takes no action against such immoral people,like your husband and his k***.Pray to God that in your next life,you get reborn in a more advanced country where the judicial system is so strong,that there is nothing to fear,if,at all,you face any injustice.
Do you have a child?
If yes,you can file DV Case against your husband where you also mention about his live-in.
If they live in a house which belongs to your husband,I think a case of tresspass can be made aginst this "bechari widow" for illegally living in your husband's house on whcih only you have the right.(Confirm from a lawyer about this action also)
This widow who's living in with him must have trapped him,your foolish husband,with the power of her tears,which many women are good at shedding,when they want to get things done their way.
Even if you don't have a kid,file DV case to demand maintenance,compensation for harassment and of course mention all his cruel behaviors,including mental cruelty such as this affair.
In India,sometimes you have to deal very strictly with an iron hand,because some people often don't understand the language of softness.Once the case is filed,obviously the name of this woman will also be on papers in court.She will automatically be embarassed,besides your husband.
I don't know if this is a legal advice or not,but many people approach the media to bring out their grievances,so that they are heard.If you do so,the exposure which your DH and his so called wife get will be enough to shaken them from their "blind love(or lust).If going to media is legal you can always say why the laws in India are so hypocritic?On one hand they claim to be helping wives,but on the other they take no action against such people as above,despite a marriage already existing.So offenders like above never "learn a lesson".
If you have the guts,please check from a good lawyer about the media thing,if it's legal.I am not a lawyer.I advised since I saw many such cases on TV/newspaper.So I advised.As they have more impact.
If your lawyer says this can be done,please go ahead and let everyone know that the child they are nurturing is also out of an illegal relationship.
For all you know,your husband will even return to you after facing society's mockery.