Money has to come from somewhere. It can't just appear. So if there is really an aunt at an agency, and she is sending checks, then she is writing checks from that company, and stealing from that company. If that is the case, then the person with whom you are in contact would be using you to launder money (hide its illegal origin) and when the aunt was caught, you would be also. If it is really being done between countries, then it might be more difficult for them to find you, but it is still illegal.
However, it is also likely that your contact may be using a common scam, as described by another answerer, that of asking for money in return for a cashier's check. Although cashier's checks were designed to be "safer" than regular checks, in that they won't bounce, if it is a fake cashier's check, it was never worth anything in the first place. When the bank tries to claim the cash from the other bank, and finds it doesn't exist, or there is no record of that check, then the effect is similar to that of a personal check bouncing: the bank will want the money back.
If you have already given a portion of that money to your contact, chances are, when your find this out, he will be long gone.
I would not have anything further to do with this person.