I'm kind of sure he actually didn't fuck the dog but it was the brother's way to fuck with him hence he doesn't remember what happens. I also think chase is going to think (for sometime at least) that he converted Josh's secondary sex, guilt himself only to find out that he's been an omega all along causing 3rd act breakup only to have the baby (pete) bring them together.
I'm kind of sure he actually didn't fuck the dog but it was the brother's way to fuck with him hence he doesn't remember what happens. I also think chase is going to think (for sometime at least) that he converted Josh's secondary sex, guilt himself only to find out that he's been an omega all along causing 3rd act breakup only to have the baby (pete) bring them together.