Certified Mail Question

I know I can get the answer to this question at my local post office, but I thought I’d ask on here first.
If you send something certified, with return receipt, do you need to put a return address on it?
My wife is the administrator of her mothers estate and needs to send a certified check to her (my wife’s) brother. We want nothing to do with him, nor do we want him to know where we live. We just need to fulfill the obligation.
He disappeared when his mother was dying last September. He has resurfaced in text messages. He smells money.