The disgusting brother why is he so obsessed with bro's sex life??? Eeeeeeyuck!!! Is this ...

He has some serious mental issues bcoz of his own trauma and bcoz of how he has grown up...It was explained in his novel that he really loves Chase and did everything for the sake of chase too - He just really don't understand that it's not helping, but abuse...But well I don't care either...I also hate him and he can just k!ll himself

Because his brother cares for Chase in his own messed up way. That is sadly the truth.
You understand what it means to be a dominant alpha in this universe?
Those pheromones gives them advantages, but they are like poison, can damage their brain. They need to release pheromones, or they will sooner or later damage their brain and go insane.
And Chase is not releasing pheromones on his own, in no way. If they need to get him to those parties to use an injection, that means that Chase doesn't getting one on his own.
Grayson, and that is a spoiler, is a born manifested. The extremest form, and because of that has several issues, problems understanding emotions etc.
Their dad, that is also a spoiler, lost the ability to feel emotions due to pheromone accumulation. So their dad hammered into his childrens' brains that they need to release pheromones regulary.
Chase, who manifested later than his siblings has emotions, but can lose them or go insane, when he doesn't release pheromones.
So Grayson does that to help Chase, at the same time Grayson's methods caused a massive trauma on Chase. The question is why doesn't Chase take care of it on his own or why does their dad let Grayson take care of it, since he knows how problematic Grayson's help can be, is aware of the dog incident and monitors all his children.

This is a grown man and he ought to realise just how much he has traumatised chase. He made him believe he fucked a dog and never clarified to him about anything. All for his well being my ass what about his psychological well-being being doesn't that matter too? Keep his body well but fucking with his mind defeats the purpose he's a controlling piece of shit. He's the reason josh and chase had sex in the first place high on pheromones when even without it they have proper chemistry.

What does being a grown man has to do with it?
Do you think that they are normal? Because they aren't. And I hate to burst your bubble, but Chase isn't normal either. What do you think people that are not Josh think about Chase? And with reason.

All dominant alphas in that universe are psychopaths, that's how the author wants them to be. How many issues they have depends on when they manifest, and they can become more if that don't release pheromones regulary. So you could say that Chase got lucky, but he still has anger and violence issues.
I actually don't want to go into further details about Grayson and the Miller family, because of spoilers.
The main reason why I answer to those kind of questions here is, that most here ignore the rules of this universe. And in parts the manhwa adaption is responsible for that.
Just to make this clear, there is no question about it that Chase and others suffered because of Grayson's "help".

No, he isn't the reason for Josh and Chase having sex the first time. From the very beginning Chase didn't want to sleep with others without emotions, so he let his pheromones build up and did not release them on his own. But Josh came across him when it resulted in a rut, and Josh was fully contious, he knew what he was doing. The one that wasn't was Chase.
Sorry, but Grayson is not responsible for everything. Chase also has his own character, there are more family members, society and manifesting as a dominant alpha also plays a big role. Add he is a Miller, means an extra portion of delulu. But Grayson certainly gave Chase some serious trauma, that is also a fact.

Grayson as in KMIYC is still not aware of what he did to Chase. And the author wants him to be like this. Grayson's story is chronologically the last Miller story, it plays a few years later. But it is also the first story the author came up with, thats what she wrote last year. And that it is true is also clear, from the very beginning it was known how many stories were planned, even the titles. And especially the Grayson x Dane pairing was known. So Grayson in Kiss me liar and Kiss me if you can is like she wanted him to during that time, saving his character development for his own story.

That’s really messed up but still doesn’t excuse the fact with the dog…and many incidents from his childhood like when Chase got into an accident bcoz of Grayson…Yeah, I understood he isn’t mentally stable, but that has nothing to do with Chase…Just like chase is responsible for every toxic acts he did with others who had nothing to do with his mental issues, Grayson is responsible for his own actions towards Chase too…So, hating on Grayson is totally reasonable…Even the most heinous criminals in real worlds are just ppl with mental issues and traumas who nvr got any help…So, it doesn’t really matter what’s ur reasons behind was, it’s the action that speaks. And no one can take accountability for anyone else. Yes Grayson did everything for the sake of Chase, but he traumatised him for life and so his help has no meaning. If Chase had died, he would have just suffered for a less time. Well, by the universe did u mean just this manhwa or all other omegaverse? Bcoz in other omegaverse, alphas can control themselves well~ Yeah this one is just too messed up.