OK. Before his stay expires, he would have to file an I-539 which can be found here:
He would have to explain the following:
1) How much time he needs.
2) Why he needs so much time.
3) Why he couldn't do what she needed to do during the first 6 months he had.
4) How he would be supporting himself for this additional time since he is not allowed to work.
5) What STRONG ties he has to his home country to ensure that he will go back.
6) What preparations he has made to go back.
As long as the I-539 is filed before the stay expires, staying in the U.S. after the stay expires is legal while the I-539 is pending.
My goal is to provide you with excellent service – but we are NOT done if you need to continue. If you feel you have received anything less than excellent service or you just simply have additional questions, please reply back as I am happy to address a few (within a reasonable limit) follow-up questions for you and there is no additional charge. Also, should you need help reviewing documentation or additional services outside of this website, we can upgrade the service to communicate in private about that.