All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The fact that the spouses live apart from each other does not lead by itself to divorce even if they stay separated for a long period of time as we clarified in Fataawa 82732 and 89825. Besides, a husband is not permitted to be absent from his wife for more than six months except with her consent. If he is absent from her for more than six months and she is harmed by it, she has the right to ask for divorce as clarified in Fatwa 88495. So, she may take her case to an Islamic judge so that he would look into the matter and remove the harm from her by divorcing her from her husband or getting a Khul’ for her.
As regards Zina (fornication or adultery), then she is not permitted to come near it at all. Rather, a wife must protect her chastity and protect her private parts whether her husband is present or absent from her. Zina is a grave major sin and the absence of the husband from his wife is not a sound excuse for her to commit Zina. If this happens from a married woman, then this is even more forbidden (than its being committed by an unmarried woman). For more benefit, please refer to Fataawa 85254 and 85425.
Finally, we would like to mention the following matters:
1- What is important in the marriage contract is to identify the spouses in a way that they are distinguished from other people in front of the witnesses. So. if the two spouses are known, then changing the names does not affect the validity of marriage, as it is the persons that are taken into account and not the names. For more benefit, please refer to Fatwa 129813.
2- A husband is not obliged to inform his second wife of his first marriage as discussed in Fatwa 86395.
Allaah Knows best.