All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If a man marries a woman without a guardian or witnesses, and they both concealed this marriage, then it is of the type of marriage agreed upon by the scholars that it is invalid.
Ibn Taymiyyah said: “If he marries her without a guardian and without witnesses and they both concealed the marriage, then this is an invalid marriage according to the agreement of the scholars….” [End of quote]
Therefore, this marriage does not require a divorce because it has not taken place at the first place. However, if you marry someone else, then two different men would each claim that he is your husband, so you will be involved in troubles and legal accountability. Hence, you should avoid this, and take the necessary measures that would prevent this.
Finally, we would like to point out to the following two matters:
1- The mere fact that a man has already been married is neither an Islamic nor a customary impediment that prevents a woman from marrying him.
2- It is a duty upon the Muslim to ask the scholars about the Sharee’ah rulings that he does not know before saying anything or undertaking to do anything as Allah Says (what means): {So ask the people of the message if you do not know.} [Quran 16:43]
For more benefit on a woman’s marriage without guardian, please refer to Fataawa 92758, 132754, and 81777.
For more benefit on the ruling on whether a defective marriage requires a divorce to be terminated, please refer to Fatwa 313549.
For more benefit on the conditions of a valid marriage, please refer to Fatwa 83629.
Allah Knows best.