That's great! Your coworker's family member is breaking the law! You can't sublet for more than the rent controlled rent.
I'm surrounded by law-breakers then. https://www.kijiji.ca/b-short-term-rental/gta-greater-toront...
It's rampant here in SF as well. I know a few folks who are getting 2-3x their total rent payment by renting out a couple rooms.