Adopted incest pet play is just so fun <3 Jon so Very normal about the idea that he might fail/disappoint his father (the only adult who ever seemed to really understand him. To want him) and developing a fetish about it. What if he was just Elias’ treasured puppy who didn’t need to be smart or worthy or feel constantly at risk of losing the one and only person he has. What if he didn’t need to feel guilty or ashamed about how badly he wants Elias to have sex with him (or think about how he specifically wants Elias to desire him). He’s just a dog and it’s ok if he needs to sit in Elias’ lap and hump his leg. He’s just a dog he doesn’t know any better.
I sort of want Elias to be a little blindsided by this development too btw. Obviously he’s already aware of Jon’s fears and insecurities and Issues but the kink part should be a surprise to him. Maybe he was very busy at work and Jon was off at uni, so he doesn’t expect it when, on Jon’s first holiday back, he is near-constantly thinking about how awful and disgusting it is that he wants Elias to put a collar on him and call him a dog.
Needless to say, Elias finds this new development fascinating.