Civil suit against guarantor’s legal heir

This is regarding the case wherein a public bank filed a case on the legal heir of deceased guarantor in 2013. The loan was sanctioned to a proprietorship firm. The firm & its proprietor was unknown to guarantor’s legal heir. Details of the case 1.A public bank sanctioned a loan for the amount of Rs 5lacs to a proprietorship firm for the electric generator under CGTSME scheme in April 2011. My Father had given the personal guarantee in that loan. 2.My father died on July 2011. The new guarantor was not appointed by bank even after knowing the death of my father. Legal heir does not inherit any movable or immovable asset. 3.The loan account was operated by the borrower till July 2012. 4.The loan account became NPA by bank on Oct 2012. 5.Bank filed legal suit for recovery of amount Rs 4.5 lacs including interest in the court of District Judge on Oct 2013 6.There are total three parties in the case (Firm, Firm’s proprietor and me). 7.Borrower is not traceable and all the documents in the case (like borrower ID card/Pan card/ Firm’s address) are fake. 8.Loan was sanctioned by bank in one day after receiving the loan request from the borrower. Please suggest, Any solution so that I will be removed from this case. Do I liable to pay the loan amount, if so, up to what amount. Any other suggestions/opinion