It's actually the opposite, but Grayson is a born manifested dominant alpha which is extremely rare, but is the worst that can happen. He has problems recognizing emotions in himself and others, lacks emphaty because of that, his logic works a bit different, etc. And he was trained to mimick emotions which leads to those misplaced creepy smiles. Let's say he has a lot of issues.
He is really convinced that what he does helps Chase.
In his own story, novel only at moment, you get his pov. You can read there what's wrong with him.
It will be explained the next time Josh runs into Grayson, which should happen soon, buf if you want to know now....Spoiler ...............................................................................................................................................................................................................................................................
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When Chase had his first rut, Grayson was present and panicked (pheromone accumulation is very dangerous for dominant alphas), so he brought his dog, but Chase passed out nothing happened. They took out Chase pheromones with an injection (why suddenly an injection? in KMIYC there was no explanation, but in DMIYC we find out that their dad arrived saw what happened. He used injections for 10 years in the past).
The problem is that Chase can't really remember that rut, but that there was a dog present. And Grayson lies and uses Chase's fear of losing controle to make him go get rid of his pheromones ( to those parties, where they after Chase passes our use an injection to get rid of his pheromones) since Chase is not doing that on his own.
Same is the talking about their brother, after I started reading some of Bliss's novel, I can't imagine one of his siblings doing anything to him, but their dad is extremely paranoid and thinks the worst about his domiant alpha children. And Bliss is a dominant omega.
But the pheromone/instinct thing is a reality in this universe, so those kind of things are most likely not baseless there.
Bliss's webnovel is currently in progress, the titel: "Deflower me if you can"
His pair is Cassian Strickland, he is an earl (son of a Duke) who lives in England. The age gap is pretty big, Cassian is 11-12 years older than Bliss and they first met when Bliss was 6 years old. He is a beta, but it's possible that Bliss unintentionally started to mutate him, when he manifested as a child. It's still not clear, since he still is a beta, but he had insomina after the last time he spend time with Bliss during his manifestation, and that was 10 years ago.
And to all those complaining here about the poor omega brother, he is the most pampered, spoiled, and loved member of the family. You'll feel even more sorry for Chase when you read that, I certainly did. Currently it is set in the same time as KMIYC, RAIYC, and KML, when it was mentioned that Bliss was send to England in KMIYC.
The author is thinking about the Spencer-Pete-Cecil situation, since so many fans are interested. But I don't think that this will happen before she is finished with the 5 "Kiss me..." stories she didn't release so far/ done with the current generation. Since that story would most likely be affected/ affect the "...if you can" and "Kiss me..."series.

What is wrong with Grayson? does he hate his brother or something