Ms. Surekha, Advocate Amita Virkar is absolutely right. If you do not get marriage certificate of 2nd marriage of your husband, then you can take witness of the persons who were present at the marriage ceremony. Also, you may find out any record that he has been converted to Muslim religion. Even after getting the birth certificate of the child borne out of 2nd marriage of your husband, that will establish that your husband has got a child from that girl. However, it will not prove the fact that your husband has married that girl, which you will have to prove specifically and beyond all reasonable doubts.