We are two sisters (both married) without a brother. My parents are alive and own a house in Islamabad as well as some property in UK. My father has one sister and four brothers and his mother is alive too. He was sharing with me his will a while ago which says that after he expires, if our mother lives in the house which he has built for themselves, we, the sisters must do let her by buying the shares of my father's brothers as per Islamic inheritance laws. I would like to know what exactly does Islam prescribe in this case as it seems so cruel to me that my mother will have to vacate her house if she is unable to buy the share of my father's brothers. Could you please throw some light on this particular case?