You have not mentioned that what nature of property is held by your father in law, i.e., whether it is ancestral or self acquired or inherited from his father as share in a partition or gift deed or settlement etc.
Assuming it to be self acquired property, your father in law has full rights in the property to disposed the same in the manner and desire as per his choice and sweet will and wish. In that no one including his wife or your wife has any rights to claim anything or even a share in it.
If your father in law is holding ancestral property then as on this date your wife can claim a share outof his share in the ancestral property.
So clarify other issues and revert.