yeah i think since chap 15?
SPOILER
So I read the novel a while back but if I remember correctly Chase still doesn’t remember it was Joshua he slept with. In fact, I think right now he believes he is only confusing him with that night, with his already fuzzy memory. Because right now Chase thinks he slept with a dog, due to the fact that it is what his brother wants him to believe. Which is why he is so scared of them because he thinks he might loose control again and the accident with the dog might repeat itself. In fact, Chase has a slight suspicion that it wasn’t a dog that night but a person. And has showed interest in finding them because even he thinks it wasn’t right with what happened. But his brother stops him every time and reminds him it was a dog not a human. The reason Chase can’t remember is because he hates his own alpha traits so much he suppresses his pheromones with a bunch of medication to the point that it’s killing him. Which has long term effects on him such as when he lost control and slept with Joshua that night and forgot most of it. In fact, when he finally does realize it was Joshua that night he freaks out till the point of crying because he thinks he raped him that night and pushes him away. Joshua denies that Chase rapped him because according to him the night Josh chose to sleep with him willingly. If anything Chase suffers badly from depression and with his identity as an alpha. He hates the needs and traits that comes with being an alpha. Which is why he is so spiteful to everyone around him because they think all they see is a dominant alpha, something exotic not a human.
So he already knows??