The best thing you can do at this point is to get a good criminal defense lawyer and consult with a good immigration lawyer. "How can we keep him here" is a question that requires a detailed consultation and analysis before it can be properly answered.
My response to your question is general in nature, as I don't know all of the facts of your case. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. In addition, my answer does not create an attorney/client relationship.
You need to hire an immigration attorney to deal with his immigration problems. We could not help you even if we wanted to. This case would required a hand-on approach, which cannot be offered in virtual space.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.
You and your brother need the advice of inexperienced immigration lawyer. If you want any reasonable chance for him to remain in the USA you likely will need to spend some money and hire an immigration attorney.
The person who posted this question, as well as anyone else who reads this response, should understand that the response is not, and should not be understood as, legal advice. Rather, it is legal information, based on the abbreviated facts presented. Immigration law is very complex, unfortunately, and immigration status adjudications are highly fact-dependent. The reader should retain an experienced immigration lawyer to analyze the facts specific to his/her particular situation to obtain “legal advice”; which this is not. Any answers offered on Avvo are of a general nature and informational only, and are not meant to create an attorney-client relationship.