Security and Legal aspects of property in Kolkata

My father in law are 3 brothers. They purchased a property in 1954. In 1968 my father in law gifted his share to the youngest brother. In 1991 the eldest brother expired. Both the eldest and youngest brother did not marry. My father in law has 2 daughters. The younger daughter is my wife and we have one son. The elder daughter has no issues. My father in law's youngest brother recently gifted his share to my father in law since he has no legal heir BUT he wanted his share to gift to my wife. Due to financial problems we could not directly transfer the property in my wife's name. In this context my wife deserves 3/4th of the property and the remaining 1/4th of the property should be equally distributed to my wife and her elder sister. My father in law probably will equally distribute the property in both of his daughter's name or he can gift the property to my son ( I think my wife's elder sister will give no objection here) . But if my father in law gifts the property to my son then my wife's elder sister may object. I also do not think my father in law will do anything without considering his daughters security. If my father in law gifts the property to my son , can we have some measures to control the property . I am concerned since my wife's elder sister has no legal heir , so in her absence will her share of property go automatically to her husband. In that case we loose that part of the property.Can you please suggest me how we can secure the property so that my father in law feels secured about his daughters future , my wife ( or son) also gets 3/4th of the share , ways to protect the property to go out of our hand.