If I have a customer who came in to cash a check, not drawn on us, for $10,500 and requested that we split the cash up in 2 envelopes with $7590.00 and $2,910.00 because he needs to give the $7590 to his brother. His brother is also a customer, but was not present. Should both of them go on the CTR?

IMO you don't really know what he's ultimately going to do with those funds, I was always taught you file on whomever is directly in front of you - who you're handing the cash to. I would not include the brother on the CTR.

I would also only list the customer that cashed the check. There are cases where we may know a customer is transacting on behalf of someone else, and in those cases we would list that third party, but I make a distinction between conducting a transaction on someone else's behalf and conducting a transaction that will ultimately be paid to someone else. The customer is taking out money on his own behalf so he can pay his brother. Similarly, if the customer was taking out the money to pay for a car, we wouldn't list the car dealership in the CTR.

That was my exact example when discussing it with other staff members here. Thank you!

first, he is on CTR as he is present, and i also wouldn't spilt it into separate envelopes, he can do that himself

If a customer asked me to split it up into two separate stated amounts, I'd do that. And supply the envelopes. I'd expect the tellers at my bank to do it, too, if asked.

But I would not add a second party to the CTR based on what this guy said to the teller. If the third party were a co-owner of the account, I'd do it, though.