Liability of deceased person's debt

I'm a Hindu female.My father died on 2019 and unmarried 2 nd elder brother of mine expired before my father on 2014.My mom ,my first elder brother and myself are the legal heirs of my dad. A case had been filed based on empty promissory note which my brother(deceased ) had signed on 2013 that my father ,my mother, and my first elder brother has to repay the 3 lakhs of dept with interest and other charges. None of us aware of the promissory note or whether he has borrowed . Neither my father or anyone from family responded to the petition . Subsequently my father died on 2019.so now they have attached my father's property. I'm also one of the legal heir of my father but not included in the case.though i was aware that someone has filed a case, i was not aware what is going on because I'm married lives in another place My mother is a legal heir of my deceased brother. my doubts are 1. my brother was unmarried when he died , and died before my father. So How many parts my father's property will be divided. 2. Are myself, my mom , my first elder brother Have any liability to repay the loan? 3. As i want to proceed this case , what is the best for me to do ?