Maternal aunt claiming right over whole property how to claim my share

There is a property in Banashankari 1st Stage, which was owned by my maternal Grandfather bearing size 50X60. He passed away in 2000 and the property was transferred to his wife (my Grandmother) in 2003. My grandfather has 3 daughters & a Son.. 1. Eldest- (My Aunt) 2. Second eldest -(My Mother) 3. Son- (Deceased) 4. Younger Daughter My aunt is a divorcee, she is residing with my grandmother (since 1998), and recently, we got to know that my aunt has signed the entire property in her name without notifying us. Back in yr-2000, my Grandmother had few debts worth Rs 20 lakhs and her monthly income was Rs.45000/- from the same property as a rent. My aunt now claims that she has cleared all the debts and helped my grandmother in recovering the property, which is not right. My aunt is not a working person and she does not have any source of income. We have already sent the notice, but we have not heard from them so far. I would now want to claim the share from the property. Advice needed.