BIG Spoiler
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He found out almost at the end of the novel main story when josh introduced chase to pete in a themepark, where accident happen where pete got lost and almost got bitten by a dog, chase who have trauma with dogs tremble but choose to save pete even tho he is also scared
Then jost founds them and shoot the dog leg before the dog launch to bite chase who is hugging pete
Josh asking chase why do you do that knowing you also scared with dog, chase said cause pete is josh child, then josh said “pete is also you child” after that josh tells chase that josh spent time with chase when he is in rut and got pregnant with pete
They will make up, chase was shaken but actually really happy. Its also the end part. No more additional story after they made up and cleared the secret. Which is kinda bummer i would've love to see more family moments. Though they did have another son shown in the other webtoon with kieth pittman's son.
Re-read it and.... yeah. Chase is that good boy forced to be a super temperamental villain at the beginning because of his own family.
He was actually a soft boy who loves animal and sensitive towards others. If only his family would care more about his feelings, he wouldn't be doing harsh things to others to protect himself from his own fears.
Being with Josh who could gave him safety and comfort through actions was what made his actual self to finally come out.

Chase will throw the pill then tell josh that he can spend his rut with him, but he is angry cause he tought josh would just fuck anybody when in heat including chase
Josh becomes angry at chase statement then accidentally breathes in too much of chase feromont then almost falls but chase catch him. Chase said “so you really are an omega”
After that josh gave a felatio to chase, and after other foreplay, they fuck
but it got cut with a next scene of how chase couldn’t concentrate while working because he only thinks of josh