In the (greedy) eyes of the law, quite possibly. Sure, your brother just repaid that loan, but sadly that doesn't mean that the cops won't seize that cash until you convince a judge that you're not a drug dealer. "Asset forfeiture" hits crooks and innocent people alike. I don't like it either, but try convincing your legislator and you'll just get some crap about "balancing liberty with the need to stop drugs, mmmkay?"

Going by that they should go after retired people and pensioners who tend to hoard the cash and not trust banks

Most people however are like ants one, ten or hundred get stepped on and nobody even notices as what they churn out still gets done by the thousands of other ants.