Property share

I live in Bengaluru. My Question: In late 70's my Father's elder sister's husband purchased a 1380sq.ft residential plot in Banashankari. After 2 -3 years of purchase, he expired and my Aunt constructed a house with her husband's money and also by taking a small amount of loan from a co-operative society. My Father and family (Myself and my Mother.I am the only daughter) came from our native and started to stay with my aunt for 14 years. Later, my father constructed a house on first floor with his own savings. My aunt gave permission to construct. It was through a letter of agreement to get the Release Deed registered.My aunt received a sum of Rs.25K from my father. Unfortunately my father fell ill and couldn't get the Release deed registered nor he didn't get any any gift deed registered.Hence, our first floor house didn't get bifurcated. Now, the issue is that my aunt has become very old and for her future she wants to sell the property. The entire house is in her name. She holds the Khatha for the entire building(GF+FF). If she sells the entire house, how much share can we get legally? Can you please advise about the percentage of our eligible share.