Soldato
Pay him the money back, then withdraw from your bank whatever interest would have accumulated and hand it over to him ? 


), you'd have to be borrowing from him at an equivalent rate of 7.5%. If your brother charged you this much, you might as well get a commercial loan / mortgage @ 5%, or whatever's available on new deals.Why on earth are you complicating thing.
Borrow the money, pay it back then give him a drink.