1. You have stood as guarantor for the loan taken by your brother,
2. You have given the blank and signed stamp paper which will be converted to a guarantee agreement,
3. the cheque will be filled up and deposited as if you have issued it for refund of the loan of your brother,
4. Actually by standing as a guarantor, you have stepped in to the shes of your brother as borrower, if he refuses to repay the loan,
5. Ask your brother to repay the loan and/or get your guarantee released by returning the cheque and stamp paper which the lender will do if and only if some one else can be offered to stand as a guarantor in your place.