Cheque Bounce cased !! Help Required

Respected Sir , My mother has taken a debt of 2,50,000 INR from one of my aunt named XYZ in 2012 , and we were paying interest till 2015 , and due to some crisis , we were not able to pay the interest , so we requested the aunt that we will clear the full amount in 4 months time.It was fine till here. ( we did not gave any proofs ) In 2015 , March , my mother with the help of this same aunt XYZ borrowed 1 lac from friend of this XYZ , and she said she will need the bank cheque , so my younger brother who is a central government employee , he is just 22 yrs old , has given a blank cheque to my mother and my mother has given it the aunt XYZ as,she was acting as the middle person.XYZ aunt did not submitted the cheque to her friend , instead she has kept with her. Now suddenly , she misued this cheque and filed a cheque bounce for 5 lacs INR , I kindly request you to help me out with your suggestions , in how to deal with this case. We gave a notice to attend the court on 18th of this month , since my brother is a central government employee , we dont want him to have any effect on his job. We tried to contcat XYZ , but she is saying only one thing , contact laywers ---thats what she is saying. Thanks.