US visa was denied twice without any reason given.

Any visa issuance by the U.S. Consular Visa Section in the home country is always discretionary and not as right. Additionally, U.S. Consulate is not obligated to provide any reasons for any visa denials as a matter of U.S. Government policy, Hiring a counsel will not assist much in that instance. Yet, the American Citizen may explore a sibling petition that may take over ten years to finalize.

Every consulate's decision on a non-immigrant visa is discretionary - the government has the right to deny the application based upon the filing. Unfortunately, they do not have to give a reason for denial, and even if they do give a reason, hiring an attorney will not change the situation. I have seen many very good applications be denied by the consulate without a reason given. Hiring an attorney in such a situation unfortunately will not change the facts.

Your friend could not possibly have applied for a non-immigrant visa for her brother. That is simply not possible. If her brother applied and was denied twice, then it is not likely that he will be issued a visa without substantial changes in his circumstances.