I'm getting scam calls now to my home phone, but specifically asking for my brother.
The only time, ever, his name would be associated with my phone number would be the time we bought GenCon tickets.

Either GenCon is selling their contact lists, or they were hacked and the info stolen.
Neither option impresses me.

Sorry. but it must be something else.  Gen Con does not sell their contact list, and it has not been hacked.

Maybe one of the hotels or something?  That stuff isn't run by GenCon, but I did seem to recall hearing about booking.com or something like that being hacked recently.