If you signed up for him under your name, Koodo considered you as the account owner and there wasn't a way to separate lines in the same account to another one. So you and your brother would have to share username and password if you would like him to check his usage himself.

thank you so much for the info! 

Unable to complete the registration when opening Self Serve account, same error keeps popping up

@zakiiiii : i recommend you create another topic of your own. The customer in this topic didn't mention any error and was likely having different issue.

Make sure you mention what the error is so we can help you out