Edited to add this link:
http://nedap.org/hotline/fdcpa-recognizing.html
It talks about the rights someone who is being collected on has, & specifically details what debt collectors can & cannot do when calling friends/family members. For example, they cannot disclose that they are attempting to collect a debt if they do not directly reach the person who owes the debt.
If you are not the person they are looking for & do not ask them to call back, they cannot call more than once.
These are regulations under the Fair Debt Collection Practices Act,
Original Post:
These bill collectors are unsuccessful in obtaining a response from your brother, so they are resorting to bullying tactics. By using the internet, they are able to find numbers of people who "might" be related.
Unfortunately, it sounds like you & your mother did confirm that you konw him.
We had this happen a couple of times - once for a family member (my stepmom of all people, why would they think me with my married name would be related to her with her maiden name??) & once for someone I'd never even heard of!
Both times I said I didn't know the person they were looking for & no one by that name was at this number. After a 2nd call from the agency, I threatened legal action for harrassment. Amazingly, never received calls again! =-)
This is becoming a more & more common practice. The companies use any resources they can to get information for following up on debts, because they don't get paid until the debts are collected.
Giving them your brother's phone # won't do any good... they probably have it! Your brother just isn't answering, or isn't following through they way they want him to.
Best advice - start acting like you are someone different (ie. not related) & say there's no one there by that name @ that number. Then get pushy & threaten if the calls persist. There are laws against harrassment by collection agencies, but until their hand is forced, they will continue to call in the hopes that it will yield them information towards payment.
So frustrating, I know! Best of luck! T.