Siblings claiming share in gifted property by father, can they do that

Hi, My father-in-law passed away a year ago. He has 1 son and 3 daughters and my wife is the youngest of all. My father-in-law has purchased a small plot and gifted it to my wife when was a minor. The documents were with him before he died. As it is time for property division, my wife's sisters are asking for the share in this one also else they want to go to Court for justice. Now the plot document is with one of the sisters of my wife and they don't want to show it until my wife signs for the division of the plot. Since it is given as a gift to my wife before years by her father, I need advice on the following: 1. By law, is it mandatory to share my wife's plot with them? 2. Incase, If it is mandatory by law - they are asking us to share it only between three sisters. Since others are also alive (my wife's brother & mother), is it required to share with them? 3. Incase, If its is NOT mandatory - how to get the documents legally from them? Thanks.