There is a concept in law of "trading off".
It basically states that it is not permissible to trade in a business using the same name/trade marks as another.
How you'd go about taking this to court, I don't know. I suspect you'd find it cheaper for your brother to rename his own business (and register it with company house this time), than effectively drag his own name through the court.
People are fundamentally stupid, and if he takes it to court, you can count on at least half the readers of your local paper to think he's the copy, and not the original.