Live-in-relationship is not illegal in India. You can live with him in a live-in-relationship. You both are adults and able to make decisions about your life. He is a married person therefore, he cannot solemnise a second marriage without divorce. But you can live together in a live-in-relationship. You have the right to choose your life partner.
Legal status of couple living in live-in-relationship
Live-in-relationship confers the status of husband-wife to the person living so if that relationship lasts for a significant period of time. Section 2(f) of The Protection of Women from Domestic Violence Act, 2005 (DV Act) recognises live-in-relationship as a nature of marriage. It protects the rights of women against any domestic violence committed in domestic relationship.
Live-in-relationship or marriage-like relationship is neither a crime nor a sin though socially unacceptable in this country. The decision to marry or not to marry or to have a heterosexual relationship is intensely personal. Live-in-relationship not just for pleasure, but for emotional and intimate relationship, so as to give emotional support, companionship and also material affection, caring etc.Indra Sarma vs. V. K. V. Sarma, (2013) 15 SCC 755
Article 15(3) and 39 of the Constitution of India also protect the rights of women who have decided to live with a person in a live-in-relationship.
The children born out of such a relationship are considered as legitimate children and have a right to get share in self acquired and ancestral property of the father. You can also claim maintenance under Section 125 of the code of criminal procedure. Your partner cannot deny alimony on the grounds of absence of marriage. Living in a marriage -like relationship confers on women the same rights as a married woman.