I took a quick look at the GetMinted site, and in addition to the Download version, there is also an instant/flash casino. The flash casino offers a 200% signup bonus, the download version a 100% bonus. I noticed that the OP twice mentioned that his play took place on the download version of the casino, but never mentioned whether or not he (or his brother) had an account on the flash version as well...and if he or the brother had ever taken the signup bonus/any bonus, on the flash version.
In any event, if he does indeed have an account also at their flash casino, then he is in direct violation of one of their terms:
The above was copied and pasted from here:
So even if him and his brother never played on the same computer on either account, if he has two accounts himself (one for each version of the casino), then that could be the problem. Especially if he took any bonus at all on the flash account. Just a thought.