My answers are as follows:
1. How can I prove that she is not his cousin. ( I have the details of her -her address)
Ans: Get a certificate from her department that she is unmarried and daughter of so and so.
2. What are the proofs I need to obtain that they are married?
Ans: If you can, appoint a private detector and get information about her family and marital status.
3. If I didnt get proof what should I do to get justice for me?
Ans: Oral evidence is sufficient and your affidavit is more than sufficient.
4. If we get proof what should I do?
Expecting a detailed reply.
Ans: You must lodge complaint with police or private complaint before Magistrate.
5. If I lodge a complaint with police stating that she has been staying with him while he prevents me from entering the quarters.
Ans: A case will be booked against both of them under the relevant provisions of IPC and Police Act.
6. Will this be of any use? She is also a govt em0loyee now she took long leave to stay with him.
Ans: Lodge complaint with her employer and also employer of your husband with a request to suspend them and to conduct departmental enquiry as they are engaged in immoral life style.
7. Both her and his parents supports this relationship.
Ans: Their names and addresses may be stated in your complaints so that they will be arrested for encouraging such immoral activities.
8. In their family ; especially girl's side considered them as couple
Ans: The Law of the land will prevail over customs of community. The law is as follows.
Section 494 in The Indian Penal Code
494. Marrying again during lifetime of husband or wife.—Whoever, having a husband or wife living, marries in any case in which such marriage is void by reason of its taking place during the life of such husband or wife, shall be punished with imprisonment of either description for a term which may extend to seven years, and shall also be liable to fine.
(Exception) —This section does not extend to any person whose marriage with such husband or wife has been declared void by a Court of competent jurisdiction, nor to any person who contracts a marriage during the life of a former husband or wife, if such husband or wife, at the time of the subsequent marriage, shall have been continually absent from such person for the space of seven years, and shall not have been heard of by such person as being alive within that time provided the person contracting such subsequent marriage shall, before such marriage takes place, inform the person with whom such marriage is contracted of the real state of facts so far as the same are within his or her knowledge.