Can sisters question the will if they have no share in the property ?

We are a Sikh family. Respected Experts, I would like to get legal advice for the below mentioned query. My father died at the age of 96 leaving unregistered will for self acquired property land and house. In the same he equally divided the land and house amongst me and my brother . I have two sisters for whom he gave twenty lakhs cash each and no share in the land or house to be given besides this. As per his last wish in the will, my mother was not given any share in the property and house since she is 93 yrs old and my father wished she shud stay in the same house with both son's to look after her equally. Upon his demise, when given to the revenue authorities for mutation of the land and house, my sisters gave an application questioning the will and asking for equal shares to them. As per them , the property should be dividedequal shares to them. As per them , the property should be divided in five shares including my mother to which my mother has strongly refused. Plz advice.