Procedure to get share in ancestral property

Am Hindu, A house acquired by my great grandfather been transferred to my grandfather after the death of great grandfather and when my grandfather died in 2003 without any will the property got divided among st my Grandmother, my father and my Bua (Maternal Aunt/Father's Only Sister). Now Suddenly my bua (Maternal Aunt/Father's Only Sister) sold the area to a builder to develop flats and appartment and when I asked for my share they denied stating that since my father has relinquished all his rights on the said property so am not eligible for any share on the said property. so it means that after the death of my grandfather my father has relinquished his rights on the property and must have given his share to my bua ..Also, Father is not maintaining his financial family duties on my Mother and my unmarried sister. So, What rights do I have against the said property in this situation? Can father relinquish his rights on ancestral property without the consent of mine and my sister?