Loan default by a family member

My sister availed a personal loan of 4lakh before 5 years from idbi without the knowledge of anyone in the family while working in icici. She took loan as she wanted to leave the job but she was contract bonded. She took the loan,left the job and left for delhi to prepare for an exam that could have given her better career prospect WITHOUT our knowledge. We only got to know about the loan after a few months when she started defaulting her EMIs and bank called on my mother's number. By then she had changed her number and none of us have been in contact ever since. We don't have her whereabouts.We tried our best but to no avail. Now after several years bank people have again started knocking at our door. My entire family have already been so depressed about the whole situation and now this adds up to it. Our family income is so low that we hardly manage hand to mouth. Please let me know at worst what action bank can take against my family and my sister? Can they try to takeover our house that is on my father's name within their legal rights?