The % of share of the son who bore all the expense amongst 3 siblings.

I belong to Sunnu Muslim Family and my question is regarding my own share of inheritance .I have a family of 1elder brother and 1 younger sister and our mother. My father died on 1998 leaving behind 1) a Flat & 2)state government job (compensation basis). As per decision taken on 1998 by the entire famiy my elder brother was given my fathers job (state government job) on the condition that he will look after all d financial needs of the family and that he will have no claim in property ie Flat ,and that the flat would be distributed between me and my younger sister . But in the year 2001 he left the house with his wife thereby not providing a single penny for family assistance. Even beat my mother when she insisted for money and after that he never visited our house nor he ever called my mother or me or my sister .. Then in the year 2004 I joined central govt job and i took over the responsibility of the house expense and my family that is my mother and younger sister.i was the only one earning in the family. Apart from monthly expense i also had to bear the expense of my mother medical treatment and operation and also i saw thru my younger sister marriage in the year 2011. To sum up my case i have given around 25 lakhs from 2004 till 2013 that includes house renovation etc etc. Recently my mother announced that she will divide the flat 50 -50% between me and my younger sister. My Question is--- I bore the expense of the house for 10 yrs and more than 25 lakhs of my hard earned money, For a flat whose worth is 50 lakh ,i have been told by my mother to pay my sister 25 lakhs ie (50%) so that the flat can be transferred on my name ..I ask what is my benefit in doing so? M i wrong in asking my mother to pay me the expenses i incured in house ie 25 lakhs and then distribute the rest of the amount amongst us siblings. The said flat is registered in my Mothers name although i paid for it in lakhs. Sir plz guide because lately i feel like i have cheated by family. Thanking you all Roshanali shaikh