Actually Jonelias monsterfucking fauxcest would go So hard. A giant dragon-like monster. Teeth huge and sharp and made for shearing through flesh. So many piercing, searching eyes, covering his body… a deadly predator fueled by unnatural power, far stronger than Elias. Exposing his vulnerable throat to him. Whining for his dad. Because maybe he could kill Elias with a single snap of his teeth, but he loves him, needs him.
Elias riding Jon’s cock while he shudders and moans and pleads for his dad. Looks up at him with those big round eyes. Elias’ cock hard and erect, dripping precum onto Jon’s pregnant belly. And that’s his son, beneath and inside of him. Pleading for him.

I feel like I’m not making my point well. Just. Just this terrifying horrible monster. Handing so much control over to Elias. Viewing him as a figure of unquestionable love and authority. Responsible for raising and protecting and punishing Jon. Elias getting off from Jon not just being his son, but from monster!Jon viewing Elias as his dad.