Share in mother in law's property

Halo sir.. i am a housewife nd got married in 2011. My father in law expired in 2009 nd he was a govt employee. Now my mother in law is the sole owner of his pension amounts nd other benefits of goVt, house, lands, gold, cash nd other properties aquired by my father in law during his lifetime nd registered them in my mother in law's name. She got two sons nd one daughter. All got married nd got children. My husband is the younger son. Now my mother in law has given all the PF amounts nd fixed deposits nd gold to my brother in law nd sister in law. Around 40 to 50 lakhs in the form of cash nd gold. If we ask anything abt this she says it is her wish to give anything to anyone she wants. If we ask for a will also for our share in house nd lands, she denies to make a will. We doubt that she does not want to give a single pie of my fathr in law's properties to My husband. Aftr her demise, if we come to know that she made a will only in favour ofmy brother in law nd sister in law means...what shal we do? Or else if she make a will just giving only a little share of the properties to us means..how can we challenge that unfavourable will of hers? Pls help me in this regard....