If you feel that the will is forged, then naturally you’ll have to contest it and show that it is a forged will.
If your father-in-law had more than one properties (as you claim), then it is possible to have different will for different property. Moreover, since your wife is also a legal heir, she should also know about other properties of her father. If she knows about other properties of her father and no will has been claimed or produced for such other properties, who has stopped her from initiating proceedings for obtaining succession certificate in respect of such properties?
Usually, every will may mention that it is the last will (in respect of the properties mentioned therein) since at the time of its preparation it would have been the last will. If you believe that it is not the last will, then you (or other interested parties) have to produce a subsequent will which might have superseded the said so-called last will. In the absence of any subsequent will being produced, such will may be accepted as the last will if found to be genuine.
Naturally, if you are not able to show that the will is fraudulent or forged, it may be accepted as genuine.
As I have already mentioned, if there is no will in respect of some properties, you may initiate proceedings for obtaining succession certificate in respect of the same. You need not wait for others to produce will in respect of such properties. If someone has a will in respect of those properties, he or she would object to such proceedings and would produce the relevant will, if any. This is what is I think.
It may be advisable for you to engage some lawyer to help you in court proceedings in view of complications suspected by you in these issues.
Dr. Ashok Dhamija is a New Delhi based Supreme Court Advocate and author of law books. Read more about him by clicking here. List of his Forum Replies. List of his other articles. List of his Quora Answers. List of his YouTube Videos.