Bank npa

SUPPOSE A B C ARE 3 BROTHER HAS FATHER F AND MOTHER M. 1. M HAS TAKEN LOAN IN 2007 FROM ALLAHABA UP GRAMIN BAN AND DIED IN 2014 HIS SON A AND B ONLY GO TO SAME BANK IN 2016 AND TAKE ANOTHER LOAN OF KCC IN INHERITED PROPERTY BETWEEN 2 BROTHER AS THERE SHARE . BOTH THE BROTHERS AND BANK WERE UNAWARE OF NPA. NOW IN 2021 BANK ASKING THEM TO PAY NPA. PRESENTLY BOTH AMOUNT ARE NPA BY M IT IS OUTSTANDING OF 4 LAKH AND BY BOTH THE BROTHERS IS 6 LAKH. MOREOVER COST OF INHERITED PROPERTY IS SUFFICIENT ENOUGH TO PAY ALL NPA. 2. IN 2004 F HAS TAKEN KCC LOAN FROM 2 BANK SBI AND ALLAHABAD UP G BANK F HAS DIED IN 2018 NOW SBI BANK TRANSFER NPA TO ITS 3 SON IN 2019 BUT ALLAHABAD UP G BANK HAS FAILED TO DO SO NOW IN 2021 FATHER ACCOUNT F HAS NPA OUTSTANDING OF 4 LAKH. MY QUESTION WHAT BANK ACTION CAN TAKE IF OTHER PARTY IS USUAL DEFAULTER?