You cannot stop anybody from proceeding against a matter they feel aggrieved.
Your account Either or Survivor and your Father passed away and you closed the account. The transaction appears to be quite above board. Even if your brothers approach the Court, you may have to show all the relevant documents and prove your point. Bank Official also may be asked to give witness duly producing the account opening form. Therefore, keep all your records with you, at least photocopies so that if and when there is a need, you can use the same.