assalam walikum,
i got married recently and i was really frustutaed with my wife behaviour. when i emphasized her, she revealed her past from the age of 8, that her maternal uncle used to lure her by giving her candies and take her to the terrace and use to do all sorts of sexual activity in the nights. this was carried every day till she realized that she is doing an wrong act, she stopped moving with him. but when he finds her alone in home he used to forcibly asked her to do and threatened her not to reveal so that the image of both will get spoil in the family. this was continued for almost 12 years (i,e) till the age of 20.
when i insisted my wife what happened after puberty all those years.did he raped you ?? she said he(the maternal uncle) used to enter the room silently ,do hug,kiss and forcilbly tried to do without opening the clothes in short span (~5mins)keepng in mind that anyone would see as their family was joint family . i am very upset after i heard this.i really itches me when i am alone and also get disturbed in my prayers.is our marraige valid ?please advise.?what should i do ?

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.

If the situation is as you mentioned in the question that the maternal uncle of this girl used to have sexual relationship with her, then he has indeed committed a grave abominable sin, because he should be protecting her honor and dignity instead of transgressing it. Therefore, he is obliged to sincerely repent to Allaah.

If she still sees from him something doubtful, then she should treat him like a non-Mahram, so she should not allow him to be in seclusion with her and the like as we clarified in Fatwa 90501.

Also, if sometimes she had consented to him about this act, then she is also obliged to repent to Allaah because she should have threatened him to disclose his matter as this may deter him instead of him threatening her.

As regards your marriage to her, if it happened fulfilling the conditions of the marriage contract, the most important of which is the presence of the guardian and two witnesses, then the marriage contract is valid. Nonetheless, you are also obliged to conceal her matter and not inform anyone about it; for more benefit, please refer to Fataawa 83573 and 83268.

However, what is important is the situation of your wife now, if you see that she is not suspicious, then you should keep her, be kind to her and have good marital relationship with her as Allaah Ordered us in His Saying (which means): {And live with them in kindness.}[Quran 4:19]

You are also wrong by asking your wife about her past, as this matter is not permissible. The consequence is that you have become stressed because of this and if you had feared Allaah in this matter, what happened to you would not have happened. Therefore, our advise to you now is to continue your life with your wife as if nothing had happened and seek refuge in Allaah from the whispers of the devil.

Finally, if you are not able to continue your life with her after getting to know what happened, then it is permissible for you to divorce her. 

Allaah Knows best.