I’m not sure if this has been mentioned, but HBCUs usually do not award much merit aid. The private ones do not have the endowments that allow widespread large merit gifts, and the public ones are public universities which will not offer much aid to OOS applicants.
I’ll hazard a guess and assume your brother applied to the “name brand” private HBCUs like Howard, Florida A&M, Morehouse, etc? Families are often surprised by the lack of aid for students at those schools, outside of some applicants with excellent stats.
There are a few public HBCUs that award significant aid. Some in Mississippi and Alabama will be generous and have explicit charts on their websites that outline the stats needed and the amount of the aid. Fayetteville State University in Fayetteville NC has a few good merit scholarships - and FSU has an arrangement with NC State University to allow Engineering students to take classes on both campuses.
Also, Elizabeth City State University in NC has a low-cost guarantee for in-state students, but the price point for OOS students is often much lower than in-state costs at some other states, especially PA.
There are more options, but it will take some hunting and research for you and your brother.