Your husband has not married the lady so no case of bigamy is made out 

adultery is no longer an offence 

Since you both are living separately for five years and also it appears that he will not rejoin you to resume the  irretrievably broken marital relationship,  you may better understand the situation and take an appropriate decision that will be suitable to the prevailing circumstances. 

There is no provision in law to book him under criminal laws for living with another woman without marrying her. 

You have right to file criminal complaint against him for offence  under Section 494 marrying again during lifetime of wife  for which  punishment is imprisonment up to seven years. Court will order police to register FIR,  investigate, produce accused in court and file charge sheet. After trial Court will punish the accused. offence  is compoundable/can be compromised. You can settle with him on your terms and compromise the case. File complaint with all proof, you can also seek DNA test of his child. That will undeniable scientific proof.

Live in relationship is not illegal and an offence of bigamy cannot be proved in this case. But still you may file a criminal complaint against the woman. Moreover, it is a ground for divorce. Also file a domestic violence case against him.

You can seek divorce from him on this ground

Hi, you can file a policy complaint for bigamy and also for adultery against your husband.

Dear Client,

               Cheating means sharing affection, both emotional and sexual, with someone else other than your wife and without her consent. It depends on the circumstances. However, this general definition is not the same as the definition of cheating under Section 415 of the Indian Penal Code, 1860 (IPC). In a case where the husband is cheating on his wife with another woman, he requests the wife to hand over her jewellery which he will use to pay his debts. But instead gives the jewellery to the woman with whom he had an illicit affair. This would amount to cheating under Section 415. Hence, this Section will not have its application in matrimonial cases.So, it can be considered that there is no liability if one party decides to leave the other partner. But the status of children born out of live-in relationship has never been clarified by the court except on a few points. In the case of Tulsa & Ors vs. Durghatiya & Ors the Supreme Court provided that the child born out of cohabitation are not to be treated as illegitimate but there are certain pre-conditions which are like the parents must have cohabited for a considerable amount of time under one roof so that the society recognizes them as husband and wife. And same has been said by the court in other cases that if a man and a woman have been cohabiting for a long period of time then they will be presumed to be legally married unless proved contrary. So, in India, there is an urgent need for legislation on the live-in relationship.

Thanks & Regards

- Since he has filed the divorce petition then you must contest the case against him ,and file an application in the same court /case for claiming maintenance 

- Further, if you agree for divorce then claim alimony and property from him , as the child from that lady having right to claim property from him after his demise.