Explain Like I'm Five

He's a beta cuck. Real alphas don't have to go around proclaiming their alpha status and receiving praise and validation from betas and other "alphas".

Your brother is on a (specifically designed and heavily funded) pipeline to being a total piece of shit (not just with misogyny, but racism, and probably queerphobia and ableism too), do what you can to get him off it. A quick search brings up what looks to be some good info to start you off:

Manosphere

Misogynistic influencers are trending right now. Defusing their message is a complex task

De-radicalising incels out of the ‘manosphere’ through Reddit

Making a Radical Misogynist: How Online Social Engagement with the Manosphere Influences Traits of Radicalization

Swallowing and spitting out the red pill: young men, vulnerability, and radicalization pathways in the manosphere

Exiting the Manosphere

There are also many youtube videos on the subject, though I haven't watched any recently, so I won't link, but look up something along the lines of "manosphere right wing pipeline" and you should see some results.

"Alpha male" basically translates to toxic masculinity, and "beta male" basically translates to anyone who respects other people in any way. It's the callsign of pieces of shit like Andrew Tate, who is a human trafficker and serial sexual abuser currently in prison awaiting trial in... I think it was Croatia?

He doesn't know what it means to be cool, so he's hoping that just declaring that he's cool will be good enough to make him popular.

The problem is that the kids who try this strategy almost universally cannot pick up on social cues, otherwise they would understand that it will always lead to the opposite result. People who seriously say out loud that they're alpha males are pretty much exclusively losers or scumbags.

Ask him if being an alpha male is a furry thing

Tell him calling himself an alpha is just what a beta would do. Real alphas don't say shit about themselves, they have people who do that for them. Watch him implode.

He’s watching toxic YouTubers like Joe Rogan and Andrew Tate.

If you want advice on how to handle this: ask questions. Ask them calmly and without any judgment. Be genuinely curious.

"What makes him a 'beta male?'"

"What characteristics do you admire most in 'alpha males?'"

"What characteristics do you think you have?"

"Where'd you learn about all this?"

Don't ask them in rapid fire, pepper a question in here and there over time.

He wants girls to think he is cool but has received bad advice

It’s called the manosphere, and it’s a bunch of bad podcasters and YouTubers giving shitty advice on how to be a man to insecure kids. It’s annoying because it’s so stupid on its face and yet it’s working.

Beat his ass to establish dominance.

Alpha quality, like software. Buggy as hell and should not be released. :D

srsly though it's the clusterfuckchild of social darwinism, grindset mentality and randroid zoology, plus a bit of wannabe-dom.

There was this old, debunked concept of the 'alpha wolf' as pack leader - all dominance displays, all the time, stronger and wiser and better than the rest, a sort of rightful-king that owes nothing to anyone, and that all lesser wolves obey and look up to.

Some absolute chuds picked up on the concept and decided that it applied to people, that it was a quality people could and should naturally embrace, unless they were just inherently inferior.

And of course they tied that all up with being male, because apparently men are just 'naturally dominant', unless again, they're broken and inferior ones - so if you are male, it's vital to prove that you're a properly functioning one by being a domineering asshole who deserves to get away with it out of sheer chutzpah, or else you deserve nothing but contempt and getting trodden on.

This ties in with conservative morality, which is entirely based around acknowledging and reinforcing social hierarchy. Right is when power is exerted downwards in the hierarchy, wrong is when power is asserted upwards.

So in this world, 'alphas' are the master race, while 'betas' are submissive half-men who lack the strength (and thus the virtue) to display the proper 'rugged independence'. They're also obsessed with 'cucks', ie cuckolds, men who lack the necessary manliness to fight off 'alphas' who would disrespect and shame them by having sex with their woman.

It's all incredibly toxic, and you need to pick him up and shake the bullshit out of him.

pic related

That tells you that he's insecure about himself

He found tate's channel.

Just tell him he's fully cuckpilled cause he clearly isn't looksmaxxing.

He is a furry that identify as a wolf. /s

How old is he?

It's a furry thing

If you're really asking what it means, an Alpha is a strong leader. They don't take commands, they give them. If they want something, they take it. They consider themselves superior to the weaker beta males, and feel that it is their duty to lead the betas, or that they are doing them a favor by pushing them to be more like an alpha.

Although, a lot of the time, the people who claim to be alphas have none of the redeeming characteristics, so they just act like entitled assholes.

EDIT. I think because I didn't come out swinging people are assuming I believe any of this shit. I was trying to explain it from the perspective of their brother. I thought they wanted to know what it was about, and just calling people assholes doesn't really explain what THEY believe.

Others have given you a lot of info here on what it is your brother is referring to.
But what this is reflecting in your brother is that he has fallen into a pipeline of watching these videos or hanging out with people that watch these videos and had some insecurities that he's dealing with that is making these ideas seem like the answer. It would be a great idea to be supportive of him in whatever other hobbies/activities he has outside of watching those videos and spending time with him. Talk with him about anything other than the content of those videos so that those thoughts aren't even entering his mind. Introduce him to your friends that are also supportive in something other than those videos (you don't mention your ages, so it's unclear if you know the same people). Having supportive people around his activities and hobbies will help him lose some of those insecurities that made him gravitate to those videos.

If that fails, what I've seen others say works is if says he's an alpha male say back "I'm not into that furry stuff, but that's really cool your so open with your sexuality like that, and accepting of others' sexualities like recognizing the beta males"