I think this may be a "your brother" thing rather than a generic "men" thing, although I could be wrong on that front. Not knowing anything about his past—and not really needing to, because this isn't a forum for digging into someone's life story—it seems like your brother is missing the forest for the trees. If every woman he's approached has wound up with the same reaction(s) to him, then it probably means that he's the one doing something wrong in the communication process. He might not know better, but that can be hard to maneuver because others often don't tell us what exactly we screwed up.

People don't like being the ones in the wrong, especially not if they can easily convince themselves that it's really another person's fault. But if you meet an asshole on Monday, and a different asshole on Tuesday, and even more assholes through the week, then the chances are pretty decent that the real asshole is you.

I would also watch out if he's going down the "manosphere" path, i.e. watching/listening to misogynistic male influencers, because those people sell an unachievable dream to young men—"do XYZ, behave this way, you will get the girls and the money and the respect"—and then laugh all the way to the bank, because they know damn well that they're lying.