Explain Like I'm Five

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

This comment section is either full of top notch satirists or the worst fucking people on Lemmy. I honestly can't tell.

How old is your brother? If he is an early teenager, it is possible that he picked these concepts up from somewhere and will very likely grow out of that thinking all by himself.

How old is he?

Every time he says it ask him if that's a furry thing.

Re-educate him & show that Alphas don't live that long

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".

The surest way to guarantee you're a beta is by calling yourself an alpha

this is great lmao what a prick

The underline issue is that human evolve to be part of social norms. Use to be a tribe, a country, a sport club. But new generation can be have more options. Associating with alpha male or whatever means he belong to a group who might like his meme or comments.

It could also be due to lack of a man figure they can associate with. So watching documentaries of strong males might help shed light on what the role could look like.

What you want is to balance his only identity or group with other (groups). For example, joining a gym, fishing, be part of musical band …. Whatever he is also into, just to get him out of that only identity he is associating with.

For me I would try to come from telling him being alpha means you can hunt or camp or survive in the wild, then lead to cooking classes or wood working. Something that mentally and physically taxing. I also would watch gordon Ramsay shows and Anthony Bourdain just to crash that image of one way to be an alpha male. You can cook and be an alpha male as the same time type thing.

Tell him you aren't interested in hearing about his omegaverse self insert

Anyone who calls themselves an "alpha" anything is a small dicked nobody.

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"

Alpha and beta? I'm released on service pack 2