Housing Loan Disbursement From Bank

I mohini murkey buyer purchased flat from seller Rajesh Kumar sing -HUF at Mira road.registration & stamp duty done but bank asking legal letter of court from seller for disbursement of loan .seller not providing same to bank as they require.in seller family son is minor.i had got sanction letter from bank.but from seller side documents not complete ,for this resion bank not doing disbursement,pl advise me how much day take to get documents from court which require to seller .seller asking me to pay late fees ,as loan disbursement is delay.bajaj & Hdfc both bank required same letter of court.he advise me go to the co operative Bank for housing loan ,but there intrest rate is higher than Bajaj& hdfc please advice me