Your brother needs to go the doctor. Do not speculate. I have GERD and it does hurt just below the breast bone. There were time when it was so severe I went to the ER. I do not have a hiatus hernia (confirmed by endoscopy). But one’s heart and lungs are there as well. Plus musculature that could be inflamed or even a stomach infection like h. Pylori might be an issue. I hope you get this resolved soon.